Inflammatory biomarkers in newly diagnosed primary care Irritable Bowel Syndrome: a subanalysis of the DOMINO Randomized Trial

Inflammatory biomarkers in newly diagnosed primary care Irritable Bowel Syndrome: a subanalysis of the DOMINO Randomized Trial | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Inflammatory biomarkers in newly diagnosed primary care Irritable Bowel Syndrome: a subanalysis of the DOMINO Randomized Trial Celine Tack, Karen Van den Houte, Linde Besard, Luc Capiau, Steven Ceulemans, and 12 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6138161/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Dec, 2025 Read the published version in BMC Gastroenterology → Version 1 posted 4 You are reading this latest preprint version Abstract Background The role of low-grade-inflammation in Irritable Bowel Syndrome (IBS) a common disorder of gut-brain interaction is unclear. Association with symptom severity, as well as effects of first line treatments are understudied. In a large cohort of primary care IBS patients (DOMINO trial), a FODMAP-lowering diet application was superior in improving symptoms compared to standard medical therapy (otilonium bromide, OB). We investigated the level of pro-inflammatory markers in this IBS cohort and its changes by the DOMINO application and OB. Methods Inflammatory markers fecal calprotectin (FC), secretory IgA (sIgA), beta-defensin 2 (HBD-2), fecal elastase (Fel-1), and C-reactive protein (CRP) were analyzed at baseline and after 8-week of treatment (diet or medication). In addition, patients filled out questionnaires to score IBS criteria (Rome IV), IBS subtypes, and symptom severity (IBS-SSS). We used Mann-Whitney-U test, Wilcoxon test, Spearman correlation, Kruskal Wallis test and Chi-square analysis to analyze our data. Results In the DOMINO trial, stool and blood samples of 445 patients were collected before and after treatment. At baseline, respectively 9, 19, 15, 20, 2% of the patients showed abnormal levels of CRP, FC, sIgA, HBD-2, and Fel-1 compared to standard thresholds. However, these markers did not correlate with IBS-SSS. In addition, CRP was significantly lower in IBS-C patients compared to other IBS subtypes. After a 8-week treatment with a FODMAP lowering diet application, both HBD-2 and FC were significantly decreased, while only HBD-2 was decreased with OB. Conclusion Inflammatory markers (FC, CRP, sIgA, HBD-2, Fel-1) were not correlated with symptom severity in a large primary care IBS cohort. All markers decreased after 8-week treatment, with significant differences for HBD-2 and FC. The anti-inflammatory effect of both treatments needs to be further investigated. Trial registration : The trial was registered with ClinicalTrials.gov (NCT04270487, registered on 2020-05-04). IBS DOMINO trial FODMAP otilonium bromide inflammatory markers Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Irritable bowel syndrome (IBS) is one of the most common functional gastro-intestinal disorders, or disorders of gut-brain interaction (DBGIs). According to Rome IV criteria, IBS is defined by recurrent abdominal pain for at least 1 day per week in the last 3 months in the absence of organic causes and associated by two of the following criteria: related to defecation and/or associated with a change in frequency and/or appearance of stool ( 1 ). The Rome IV global epidemiology study showed a worldwide IBS prevalence of 4.1% based on the internet survey ( 2 ). A representative survey in 1012 adults of the Belgian population showed a Rome IV based prevalence of 5.5% rising to 17.6% for self-reported IBS according to a general descriptive definition ( 3 ). Patients can be subdivided according to their dominant stool pattern into IBS-diarrhea (IBS-D), IBS-constipation (IBS-C), IBS-mixed (IBS-M) and IBS-unclassified (IBS-U)( 1 ). Several pathophysiological mechanisms have been implicated in IBS pathogenesis, including altered colonic motility, visceral hypersensitivity, increased mucosal permeability, imbalance of gut microbiota (dysbiosis), as well as psychological factors ( 4 , 5 ). Most recently the focus has been on low-grade inflammation in the colonic mucosa, especially in IBS-D ( 6 ). However, it is often difficult to differentiate IBS from other gastrointestinal disorders. Fecal calprotectin (FC) is a non-invasive inflammatory marker commonly used for distinguishing inflammatory bowel disease (IBD) from IBS ( 7 , 8 ). Since low-grade inflammation has been implicated in the pathophysiology of IBS, a subgroup of IBS may present with increased FC levels ( 9 ). Fecal human ß-Defensin-2 (HBD-2) has also been shown to be significantly elevated in IBS compared to ulcerated colitis, but little is known about the correlation between HBD-2 and IBS ( 10 ). In addition, several studies have reported an increase in B lymphocyte activation and by extension immunoglobulin production in IBS ( 6 ). However, mucosal B cells that are responsible for secretory immunoglobulin A (sIgA) secretion, which is important for gut mucosa protection from food antigens and pathogens, have been shown to be reduced in IBS, suggesting an altered enteral immune defense ( 11 , 12 ). Still, it remains unclear whether there is a causal relationship between reduced sIgA production and bowel symptoms ( 12 ). In addition, according to a previous UK study, 6.1% of IBS-D patients had pancreatic exocrine insufficiency defined by fecal pancreas elastase-1 (Fel-1) levels lower than 100 µg /g ( 13 ). Dietary and lifestyle changes in combination with symptom-based pharmacological treatment is considered as first-line treatment for IBS ( 14 , 15 ). In Europe, musculotropic spasmolytics are frequently prescribed and considered standard medical therapy ( 16 ). Otilonium bromide (OB), a L-type calcium channel blocker improves bloating and abdominal pain compared to placebo, with a significant response already occurring after 4 weeks of treatment ( 16 ).The role of dietary treatment is increasing in IBS, as the majority of the patients are reporting food as a trigger for their symptoms. A diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) improves IBS symptoms after 6–8 weeks. Unfortunately, due to the complexity and the requirement of a professional dietitian this is often dismissed in primary care ( 16 ). In the DOMINO trial, a self-management smartphone application was evaluated ( 16 ). This pragmatic randomized open-label parallel designed trial showed that the DOMINO application, a FODMAP-lowering diet, was superior to a spasmolytic agent (OB) in improving symptoms in a large cohort of primary care IBS patients ( 16 ). As such, a FODMAP lowering diet should be considered as a first-line treatment in primary care IBS ( 16 ). Studies showed that the low FODMAP diet reduces the levels of pro-inflammatory interleukins, fecal bacteria, total short chain fatty acids and N-butyric acid ( 17 ). Therefore, this diet might be able to diminish the low-grade inflammation and subsequently inflammatory biomarkers in some patients. In addition, some literature suggests antimicrobial actions of OB, and a potential to change gut microbiota load and composition could be associated with altered low-grade inflammation ( 18 , 19 ). Because of the suggested low-grade inflammation in IBS pathology, our aim was to explore the levels of several inflammatory markers in recently diagnosed primary care IBS patients. In addition, we aimed to investigate the potential utility of those biomarkers in the diagnosis and prediction of treatment response in this cohort. Methods Study design Current study builds upon the DOMINO trial, which is an open, pragmatic randomized parallel-group design study in which 472 Belgian primary care IBS patients were randomized between July 2018 and December 2019 (1:1 ratio) to 8 weeks of treatment with OB 40mg or a FODMAP lowering diet through a mobile smartphone application ( 16 )(Fig. 1 ). Eligible patients were newly treated IBS patients. The trial was registered with ClinicalTrials.gov (NCT04270487, registered on 2020-05-04). The diagnosis was made by primary care physicians (PCPs, n = 105). At the screening visit (visit 0) informed consent was obtained prior to any study procedures (S59482, clinicaltrial.gov). At baseline, information on patient’s demographics and IBS stool type was collected. Patients were subdivided based on their dominant stool type into IBS-D, IBS-C, IBS-M and IBS-U as defined by the clinical opinion of the PCP. Within 14 days after visit 0, patients were randomized to either OB or the smartphone application. Patients completed questionnaires at baseline, 4 weeks, and 8 weeks to score their symptoms. The consent for collection of biological samples was optional for the patients. Stool and blood samples were collected at the baseline visit (visit 1) and at the end of the 8-week treatment period (visit 2) for the analysis of inflammatory markers. Questionnaires Throughout the study, patients completed the Rome IV IBS diagnostic questionnaire to characterize patients fulfilling Rome IV criteria for IBS ( 20 ). If conform to the criteria, they are referred to as Rome +. In addition, patients completed the IBS symptom severity scale (IBS-SSS) to asses symptom severity and treatment response ( 21 ). IBS-SSS was completed at baseline (visit 1) and after 4 and 8 weeks of treatment. Patients were subdivided based on their symptom severity score: normal: 300 with a maximum achievable score of 500 ( 21 ). A responder to the allocated treatment was defined as a patient with an improvement of 50 points or more on the IBS-SSS at the end of the treatment period compared to baseline ( 16 ). Inflammatory markers All biological samples were processed by the medical laboratory CRI (Zwijnaarde, Belgium). Stool samples were analyzed to score fecal calprotectin (FC) levels (preparation by EliA Stool Extraction kit 2, ThermoFisher Scientific; ref 14-5651-01), secretory IgA (sIgA) (ELISA, thunderbolt), Beta-defensin 2 (HBD-2) (ELISA, thunderbolt), Fecal elastase (Fel-1) (ELISA, thunderbolt). C-reactive protein (CRP) (CRPL3 kit, following Roche, ref. 05172373190 instruction, Cobas 800 c702) was defined by analyzing blood samples. The biological thresholds for these markers were defined as followed: FC (> 100 µg /g), sIgA (> 5000 µg/ml), HBD-2 (> 60 ng/ml), CRP (> 5 mg/L) and for pancreatic exocrine insufficiency by pancreatic elastase (mild 200–500, moderate 100–200, severe < 100µg/g). When lab values were reported outside the measurable range by CRI laboratory (CRP < 0.3, sIgA 7500, HBD-2 < 20 and fel-1 500) by CRI using “” sign, we assumed the value to be ± 0.1 for CRP, sIgA, HBD-2 and Fel-1. Statistical analysis Data were analyzed using Graphpad Prism version 8.4.3 for OS X, GraphPad Software, La Jolla California USA, www.graphpad.com . The significance threshold was set at p < 0.05. Data are shown as mean ± SEM. Mann-whitney-U test, Wilcoxon test, Spearman correlation, Kruskal Wallis test and Chi-square analysis were used for evaluating the clinical relevance and correlation of the biomarkers with patient’s demographics, symptom severity, IBS subtype, Rome IV and treatment response. Results Patient population and baseline characteristics 459 patients were randomized, both groups were well matched (supplementary table 1 ). In this study cohort, 94% (n = 445) of patients gave consent to provide blood and stool samples. Of the 445 patients (74.6% female, 41.3 ± 0.7 years, BMI 24.58 ± 4.5, mean IBS-SSS 265.5 ± 4.6), 70% fulfilled the strict Rome IV criteria for IBS and are referred to as Rome +. The other patients had IBS according to the clinician’s opinion ( 22 ), but did not fulfill Rome criteria and are referred to as Rome -. Flow of participants and samples shown in supplementary Fig. 1. In the entire cohort, inflammatory marker levels were on average below biological thresholds (Table 1 ). Nonetheless, abnormal baseline levels were observed for FC, CRP, sIgA, and HBD-2 in 9%, 19%, 15% and 20% of the patients respectively. Only 2% of the patients showed fel-1 levels suggestive of pancreatic insufficiency when applying the predefined cut-off level. IBS-SSS at baseline was not associated with the levels of CRP (r=-0.007, p = 0.86), FC (r=-0.004, p = 0.99), sIgA (r = 0.03, p = 0.59) and HBD-2 (r=-0.074, p = 0.13). However, a significant correlation was found between BMI and CRP (r = 0.29, p = < 0.001) and FC (r = 0.11,p = 0.02), but not for HBD-2 (r=-0.02,p = 0.74), and sIgA (r = 0.02,p = 0.64). Rome IV subgroups There was no significant difference in mean biomarker values between Rome + and Rome -, except for Fel-1 (Table 1 ). Table 1 Mean levels of biomarker and Mann-Whithey-U test between Rome IV + and Rome IV- All patients (n = 445) Rome IV + (n = 308) Rome IV – (n = 129) P value (Rome IV + vs. Rome IV -) CRP (mg/L) 3.09 ± 9.24 3.11 ± 0.27 2.64 ± 0.37 0.79 FC (mg/kg) 57.71 ± 10.70 67.28 ± 15.27 34.74 ± 6.38 0.8 sIgA (µg/ml) 2415 ± 107.6 2497 ± 134.8 2225 ± 182.9 0.34 HBD-2 (ng/ml) 48.86 ± 3.34 46.06 ± 3.69 56.73 ± 7.35 0.80 Fel-1 (µg/g) 397.8 ± 5.21 402.80 ± 6.26 383.0 ± 9.78 0.03 IBS-SSS 265.5 ± 4.6 293.0 ± 4.64 199.8 ± 8.86 < 0.0001 Stool pattern Patients were divided according to their dominant stool type as follows 20% IBS-C, 28% IBS-D, 40% IBS-M and 12% IBS-U. IBS-C patients were characterized by a significantly higher IBS-SSS compared to other subtypes (Table 2). However, there was no significant difference in baseline biomarker levels found between all subtypes, except for CRP, which was significantly lower in IBS-C compared to all other subtypes (table 2). In addition, Chi-square testing showed that there is no significant relationship between the stool pattern subtype and the presence of abnormal CRP (χ² (3, N = 433) = 7.03, p = 0.07), FC (χ² (3, N = 436) = 0.26, p = 0.97), HBD-2 (χ² (3, N = 436) = 2.09, p = 0.56) and sIgA (χ² (3, N = 436) = 1,123, p = 0.77). (Fig. 2 ). Table 2. Biomarker levels in all IBS subtypes IBS-C (n = 90) IBS-D (n = 123) IBS-M (n = 177) IBS-U (n = 55) P value † CRP (mg/L) 1.99 ± 0.36 3.33 ± 0.42 3.41 ± 0.37 3.26 ± 1.05 0.007 FC (mg/kg) 53.55 ± 19.60 75.92 ± 28.77 55.47 ± 15.03 31.24 ± 5.73 0.75 sIgA (µg/ml) 2596 ± 267.00 2517 ± 200.9 2304 ± 161 2250 ± 315.9 0.71 HBD-2 (ng/ml) 53.99 ± 7.10 51.11 ± 8.39 46.75 ± 4.50 42.30 ± 6.10 0.57 IBS-SSS § 284.7 ± 9.91 263.8 ± 8.40 267.5 ± 7.52 231.8 ± 13.53 0.04 ± values are means ± SEM § Symptom severity was assessed using the IBS symptom severity scale ( 19 ). † P values are shown from Kruskal-Wallis tests comparing the four IBS stool pattern subtypes. Bold is significant. Evaluation of treatment effect In both the FODMAP-lowering diet application (n = 218) and OB (n = 227) arm, Mann-whitney test showed no significant difference between responders and non-responders at baseline (CRP (OB: p = 0.84, Diet p = 0.6), FC (OB: p = 0.70,Diet p = 0.20), sIgA (OB: p 0.55, Diet p = 0.82) and HBD-2 (OB: p = 0.19, Diet p = 0.43) (Fig. 3). After 8 weeks of treatment, stool markers FC, sIgA, and HBD-2 decreased in both study groups (Fig. 4). However, this trend was only significant for HBD-2 in both diet and OB, and for FC in the diet group (Fig. 4). As for the blood sample, CRP did decrease numerically in the diet group, but this change was not statistically significant (Fig. 4). In addition, for diet and OB no significant correlation was observed between the change in IBS-SSS (%) and changes in biomarker levels in both responders and non-responders. There was also no significant correlation between the change in FC and HBD between responders and non-responders in both arms. However, we found a small, but significant correlation between the change in FC and CRP in the responder group for medication (r = 0.24, p = 0.009), but not for diet (r = 0.15, p = 0.08). IBS-SSS at the end of the treatment period (visit 2) was not associated with the levels of CRP (r=-0.049, p = 0.34), FC (r = 0-0.04, p = 0.43), sIgA (r=-0.005, p = 0.92) and HBD-2 (r=-0.009, p = 0.86). Discussion To investigate the role of low-grade inflammation in the pathophysiology of IBS, we examined the levels of various biomarkers in biological samples from 445 primary care IBS patients of the DOMINO study ( 16 ). The DOMINO study has previously shown that IBS patients symptoms improve after 8-weeks treatment with a spasmolytic agent (OB) and a FODMAP lowering diet provided to patients though a mobile application. Moreover, IBS patients showed a significantly higher clinical response to the diet compared to the OB study arm (71% (155/218) vs 61% (133/217), p = 0.03). During this study, blood and stool samples of patients were collected at baseline and after treatment. In the current manuscript, we describe the levels of FC, sIgA, HBD-2, and Fel-1 in stool samples, and CRP in serum. We compared biological markers at baseline to standard biological thresholds and we explored plausible impact of the allocated treatment. Our study did not find a significant correlation between IBS symptom severity scores and biomarker levels in patients at baseline. We found that CRP levels were associated with BMI in our patients, which most likely reflects the known link between metabolic syndrome and inflammation( 23 ). Studies of the effect of obesity on symptom severity in IBS are ambivalent, further research is needed to evaluate a possible relation( 24 ) Both treatments did not affect the levels of CRP after 8 weeks. Several studies reported an elevated hs-CRP in IBS compared to healthy controls ( 25 ). However, only 19% showed abnormal CRP levels at baseline in our study population, thus failing to indicate significant systemic inflammation. We assessed the presence of pancreatic insufficiency by measuring Fel-1 levels and found that only 2% of the cohort had aberrant levels. While a previous study suggested considering pancreatic insufficiency in IBS-D patients, we did not observe any differences between the different IBS subtypes( 13 ). In our cohort, 9% of IBS patients had abnormal FC levels, which is lower than what has been reported in previous studies using the same cut-off level( 26 ). This highlights the importance of further investigations, such as endoscopy, to avoid misdiagnosis of IBS as inflammatory bowel disease (IBD). However, due to the pragmatic set-up of this study, further clinical investigations of the patients were not performed. HBD-2 and sIgA levels were elevated in a respectively 20 and 15% of all patients, but the literature on the relationship between these biomarkers and IBS is limited. The levels of these were not correlated with symptom severity or stool subtype in our cohort. A small study of Langhorst et al. showed elevated HBD-2 levels similar to active colitis ulcerosa patients( 10 ). Thus suggesting an activation of the mucosal innate immune system as a driver of a proinflammatory response( 10 ). The lowering FODMAP diet and OB treatments led to a decrease in biomarker levels, with HBD-2 being significantly lower in both groups and FC being reduced in the diet group. Based on the literature we can hypothesize that the observed changes in inflammatory markers may be linked to known effects on permeability in the dietary intervention, which has previously been shown for a gluten-free diet in IBS and for a low FODMAP diet in FD ( 27 ). The study of Prospero et al. also demonstrated an improvement of gut permeability after a low FODMAP diet in IBS patients by measuring markers of function/integrity of the intestinal barrier ( 28 ). Previous research has also shown that increased gut permeability can contribute to inflammation( 29 , 30 ). Further research is warranted to further explore the role of the intestinal barrier as a treatment target. Another possibility is that the higher inflammation prior to treatment could be the consequence of seeking medical attention at the time of concurrent gastrointestinal infection leading to the subsequent diagnosis of IBS. Our study is not without limitations. Post hoc analysis and not the primary endpoin, but a large number of samples. Pragmatic study, primary care IBS, no close follow up to adherence to the diet and OB intake. 8 week follow up, so long term effect is not known. Not all patients enrolled in this study fulfilled the Rome IV criteria For clinical practice it is not recommended to standard evaluation of all these biological markers. The aim of this study is mainly exploratory for the further understanding of IBS. Guidelines do recommend standard blood work with full blood count, sedimentation rate, CRP and coeliac serology as well as FC (the latter in the presence of diarrhea in a patient under 45 years of age)( 31 ). In absence of alarm symptoms and if those tests are normal, asking for further investigations should be limited and left to the physician’s informed judgment( 31 ). The Rome IV criteria applicability in primary care is being questioned, since overly rigid criteria can delay diagnosis in those patients and those criteria where primary based on secondary care patients( 31 ). Conclusion To summarize our findings, our data suggests that broad use of inflammatory biomarkers to assess symptom severity in primary care IBS patients is not recommended. Additionally, we observed a reduction in the levels of all inflammatory biomarkers in response to both treatments. Further research will be needed to establish whether this represents an anti-inflammatory effect of the dietary intervention or OB treatment, or is a bystander effect reflecting some concurrent infection that prompted patients to seek medical attention. Abbreviations DBGIs Disorders of Gut-brain interaction FC Fecal calprotectin Fel-1 Fecal pancreas elastase 1 FODMAP Fermentable oligosaccharides, disaccharides, monoasaccharides and polyols HBD-2 Human B-defensin-2 IBS Irritable Bowel Syndrome IBS-C IBS constipation subtype IBS-D IBS diarrhea subtype IBS-SSS IBS symptom severity scale IBS-M IBS mixed subtype IBS-U IBS Unclassified subtype OB Otilonium bromide PCP Primary care physician sIgA secretory Immunoglobulin A Declarations Competing interests JT has given Scientific advice to AlfaWassermann, Allergan, Christian Hansen, Danone, Grünenthal, Ironwood, Janssen, Kiowa Kirin, Menarini, Mylan, Neutec, Novartis, Noventure, Nutricia, Shionogi, Shire, Takeda, Theravance, Tramedico, Truvion, Tsumura, Zealand and Zeria pharmaceuticals, has received research support from Shire, Sofar and Tsumura, and has served on the Speaker bureau for Abbott, Allergan, AstraZeneca, Janssen, Kyowa Kirin, Menarini, Mylan, Novartis, Shire, Takeda, Truvion and Zeria. Funding was provided by a Methusalem grant from Leuven University to JT This study was supported by a research grant from the Belgian Health Care Knowledge Centre (KCE). Questionnaires in this trial were provided by the Rome Foundation research Institute. Funding The DOMINO Study was funded through the Belgian Health Care Knowledge Centre (KCE) Trials Program (study ID KCE16001), a national public funding program of non-commercial trials. KCE provided feedback on the design and conduct of the study but was not involved in the collection, management, analysis, or interpretation of the data. KCE provided comments on the drafted clinical study report and the manuscript for publication, but no publication restrictions apply. Acknowledgments This study was supported by the Belgian Health Care Knowledge Centre, in collaboration with Nelle Stocquart and Hilde Nevens and by the Rome Foundation Research Institute. Karen Van den Houte is supported by a PDM funding obtained by the Internal Funds KU Leuven. This study was conducted in collaboration with Cerba Healthcare Belgium – Labo CRI, Zwijnaarde, Belgium for the collection and analysis of biological samples. Stool analysis were conducted in collaboration with Rega Institute, KULeuven, Belgium and Mylan, Belgium. The DOMINO application was developed by EverywhereIM (Amsterdam, The Netherlands). We would like to thank and acknowledge the 105 Belgian primary care physicians for their good performance and commitment in this trial as well as the 472 participating patients. The list of recruited study investigators is attached in the addendum. Ethics approval and consent to participate This study involves human participants and was approved by the Ethical Committee Research UZ/KU Leuven (S59482). Participants gave informed consent to participate in the study before taking part. Consent for publication Not applicable Availability of data and materials The datasets analyzed during the current study are available from the corresponding author on reasonable request. Author’s contributions Study conception and design : FC and JT; Data collection: CT, KVdH, LB, FC, JT, LC, SC, OG, SM, CP, WR, JS, JR, RVB, OV, SVS and BG; Analysis and interpretation of results: CT, KVdH, FC, JR, BG and JT; Draft manuscript: CT, KVdH, FC and JT. All authors reviewed the results and approved the final version of the manuscript. References Mearin F, Lacy BE, Chang L, Chey WD, Lembo AJ, Simren M et al. Bowel Disorders Gastroenterol. 2016. Sperber AD, Bangdiwala SI, Drossman DA, Ghoshal UC, Simren M, Tack J, et al. Worldwide Prevalence and Burden of Functional Gastrointestinal Disorders, Results of Rome Foundation Global Study. Gastroenterology. 2021;160(1):99–e1143. Van den Houte K, Carbone F, Pannemans J, Corsetti M, Fischler B, Piessevaux H, et al. 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Obesity and irritable bowel syndrome: a comprehensive review. Gastroenterol Hepatol (N Y). 2014;10(7):411–6. Hod K, Ringel-Kulka T, Martin CF, Maharshak N, Ringel Y. High-sensitive C-Reactive Protein as a Marker for Inflammation in Irritable Bowel Syndrome. J Clin Gastroenterol. 2016;50(3):227–32. Hod K, Sperber AD, Ron Y, Boaz M, Dickman R, Berliner S et al. A double-blind, placebo-controlled study to assess the effect of a probiotic mixture on symptoms and inflammatory markers in women with diarrhea-predominant IBS. Neurogastroenterol Motil. 2017;29(7). Vazquez-Roque MI, Camilleri M, Smyrk T, Murray JA, Marietta E, O'Neill J, et al. A controlled trial of gluten-free diet in patients with irritable bowel syndrome-diarrhea: effects on bowel frequency and intestinal function. Gastroenterology. 2013;144(5):903–11. e3. Prospero L, Riezzo G, Linsalata M, Orlando A, D’Attoma B, Russo F. Psychological and Gastrointestinal Symptoms of Patients with Irritable Bowel Syndrome Undergoing a Low-FODMAP Diet: The Role of the Intestinal Barrier. Nutrients. 2021;13(7):2469. Camilleri M, Lasch K, Zhou W. Irritable bowel syndrome: methods, mechanisms, and pathophysiology. The confluence of increased permeability, inflammation, and pain in irritable bowel syndrome. Am J Physiol Gastrointest Liver Physiol. 2012;303(7):G775–85. Camilleri M, Boeckxstaens G. Irritable bowel syndrome: treatment based on pathophysiology and biomarkers. Gut. 2023;72(3):590–9. Vasant DH, Paine PA, Black CJ, Houghton LA, Everitt HA, Corsetti M, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut. 2021;70(7):1214–40. Additional Declarations Competing interest reported. JT has given Scientific advice to AlfaWassermann, Allergan, Christian Hansen, Danone, Grünenthal, Ironwood, Janssen, Kiowa Kirin, Menarini, Mylan, Neutec, Novartis, Noventure, Nutricia, Shionogi, Shire, Takeda, Theravance, Tramedico, Truvion, Tsumura, Zealand and Zeria pharmaceuticals, has received research support from Shire, Sofar and Tsumura, and has served on the Speaker bureau for Abbott, Allergan, AstraZeneca, Janssen, Kyowa Kirin, Menarini, Mylan, Novartis, Shire, Takeda, Truvion and Zeria. Funding was provided by a Methusalem grant from Leuven University to JT This study was supported by a research grant from the Belgian Health Care Knowledge Centre (KCE). Questionnaires in this trial were provided by the Rome Foundation research Institute. Supplementary Files Supplementaryfiguresconsortdiagramanddemographic.doc Cite Share Download PDF Status: Published Journal Publication published 23 Dec, 2025 Read the published version in BMC Gastroenterology → Version 1 posted Editorial decision: Revision requested 07 Mar, 2025 Editor assigned by journal 06 Mar, 2025 Submission checks completed at journal 06 Mar, 2025 First submitted to journal 02 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6138161","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":425583817,"identity":"32d4af08-4722-43ce-818c-b1d290888953","order_by":0,"name":"Celine Tack","email":"","orcid":"","institution":"Translational Research Center for Gastrointestinal disorders, KU Leuven","correspondingAuthor":false,"prefix":"","firstName":"Celine","middleName":"","lastName":"Tack","suffix":""},{"id":425583818,"identity":"a29d064c-b767-449d-8f4b-da02ac79479b","order_by":1,"name":"Karen Van den Houte","email":"","orcid":"","institution":"Translational Research Center for Gastrointestinal disorders, KU Leuven","correspondingAuthor":false,"prefix":"","firstName":"Karen","middleName":"Van den","lastName":"Houte","suffix":""},{"id":425583819,"identity":"f843f083-f875-4ec8-9f5a-de9821a6ce2e","order_by":2,"name":"Linde Besard","email":"","orcid":"","institution":"Gastroenterology/Hepatology Unit, Leuven, Leuven University Hospitals","correspondingAuthor":false,"prefix":"","firstName":"Linde","middleName":"","lastName":"Besard","suffix":""},{"id":425583820,"identity":"ec32b94f-7250-4788-bbce-3034103a2cb3","order_by":3,"name":"Luc Capiau","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Luc","middleName":"","lastName":"Capiau","suffix":""},{"id":425583821,"identity":"0570de71-0025-40a7-8cf9-97c9ad72fd8e","order_by":4,"name":"Steven Ceulemans","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Steven","middleName":"","lastName":"Ceulemans","suffix":""},{"id":425583822,"identity":"6baf82d3-6209-43e7-90be-46c6f8c62f5c","order_by":5,"name":"Olivier Gernay","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Olivier","middleName":"","lastName":"Gernay","suffix":""},{"id":425583823,"identity":"fedf6f8b-c4aa-4f5d-addc-1332360402da","order_by":6,"name":"Sophie Maes","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Sophie","middleName":"","lastName":"Maes","suffix":""},{"id":425583824,"identity":"77e68830-e980-4e81-a3da-48e8ccb39dd0","order_by":7,"name":"Christian Peetermans","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Christian","middleName":"","lastName":"Peetermans","suffix":""},{"id":425583825,"identity":"fb1f5b52-cc8c-46f1-95ab-46cbc8067307","order_by":8,"name":"Willem Raat","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Willem","middleName":"","lastName":"Raat","suffix":""},{"id":425583826,"identity":"6c369a90-c6e2-4a9a-8f6a-db96ee98da52","order_by":9,"name":"Jeroen Stubbe","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Jeroen","middleName":"","lastName":"Stubbe","suffix":""},{"id":425583827,"identity":"17ea69d3-4cbc-42e9-93e6-396555c11f8f","order_by":10,"name":"Rudy Van Boxstael","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Rudy","middleName":"Van","lastName":"Boxstael","suffix":""},{"id":425583828,"identity":"5156793a-8fd5-49bc-adb8-e626c777dcfe","order_by":11,"name":"Olivia Vandeput","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Olivia","middleName":"","lastName":"Vandeput","suffix":""},{"id":425583829,"identity":"6ad69385-89d5-404e-aa9f-4d0284a9e0ed","order_by":12,"name":"Sophie Van Steenbergen","email":"","orcid":"","institution":"Primary care physician, DOMINO primary care physician study group","correspondingAuthor":false,"prefix":"","firstName":"Sophie","middleName":"Van","lastName":"Steenbergen","suffix":""},{"id":425583830,"identity":"8a1ced86-e5a6-4803-ab48-0b5b99ceb899","order_by":13,"name":"Bjorn Gehesquière","email":"","orcid":"","institution":"Cerba Healthcare Belgium - Labo CRI","correspondingAuthor":false,"prefix":"","firstName":"Bjorn","middleName":"","lastName":"Gehesquière","suffix":""},{"id":425583831,"identity":"4f54ec2c-2bd9-44a2-916e-d33cf44c654f","order_by":14,"name":"Jeroen Raes","email":"","orcid":"","institution":"Department of Microbiology and Immunology, KU Leuven","correspondingAuthor":false,"prefix":"","firstName":"Jeroen","middleName":"","lastName":"Raes","suffix":""},{"id":425583832,"identity":"e58164ae-7d0a-4220-b9d1-56995e8ccdd8","order_by":15,"name":"Jan Tack","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIiWNgGAWjYBACxgYIbcDPw8B4AMLmIUILUKmBZA+YJkILGIC0GJwhVgtz+9kDzB9q7IyNz5wxOPCx7bCcOQPvwQd4HdaTl8Bw4FiymdnZHoODM9sOG1s28CUb4PdLjgHDAbYDNmbneQwO87alJW44wGMmgVdL/xugln8HbIz7gVr+tqXVA7WY/8CrZQbQloNtB8wMeHsMDjO22SQYAG3BpwOo5Y3BgbN9ycYSZ44VHOw5Z2O44TBfMl6HGfbnGD6o+GZn2N+TvPHBjzIJeYPjvQc/4NXSAI8OGGDG6ywGBnkC8qNgFIyCUTAKGBgAEBpO6iPDoSIAAAAASUVORK5CYII=","orcid":"","institution":"Translational Research Center for Gastrointestinal disorders, KU Leuven","correspondingAuthor":true,"prefix":"","firstName":"Jan","middleName":"","lastName":"Tack","suffix":""},{"id":425583833,"identity":"1e5ea7d9-62c7-45ef-8517-4e3437e21114","order_by":16,"name":"Florencia Carbone","email":"","orcid":"","institution":"Gastroenterology/Hepatology Unit, Leuven, Leuven University Hospitals","correspondingAuthor":false,"prefix":"","firstName":"Florencia","middleName":"","lastName":"Carbone","suffix":""}],"badges":[],"createdAt":"2025-03-02 08:23:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6138161/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6138161/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12876-025-04494-7","type":"published","date":"2025-12-23T15:57:53+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":78229576,"identity":"c144d1d7-ff61-4ebe-bd9e-9144a2022b7c","added_by":"auto","created_at":"2025-03-11 07:22:00","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":107226,"visible":true,"origin":"","legend":"\u003cp\u003eStudy Design\u003c/p\u003e","description":"","filename":"floatimage119.png","url":"https://assets-eu.researchsquare.com/files/rs-6138161/v1/3e7dacf767afcdd2c1dc18b5.png"},{"id":78229560,"identity":"b218505a-b8e7-484a-b574-d1a0851d8978","added_by":"auto","created_at":"2025-03-11 07:22:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":5879,"visible":true,"origin":"","legend":"\u003cp\u003ePercentage of patients per stool pattern subtype with abnormal biomarker level.\u003c/p\u003e\n\u003cp\u003e* For FC, the cut-off value \u0026gt;100 mg /kg was used\u003c/p\u003e","description":"","filename":"Onlinedrawingimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6138161/v1/eed541760c803983d1e743c6.png"},{"id":78229561,"identity":"58862502-a069-4e69-8e6d-60c23c4ee3b5","added_by":"auto","created_at":"2025-03-11 07:22:00","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":70089,"visible":true,"origin":"","legend":"\u003cp\u003eMann-Whitney test was performed for comparison of mean biomarker levels at baseline between responders and non-responders in both study arms. No statistically significant difference (‘ n.s.’, p\u0026lt;0.05) was found between groups.\u003c/p\u003e","description":"","filename":"floatimage39.png","url":"https://assets-eu.researchsquare.com/files/rs-6138161/v1/98cf7b9beb6e192d2b99701a.png"},{"id":78230777,"identity":"30ccbb06-ac81-4c7c-8f94-351d4a4ebada","added_by":"auto","created_at":"2025-03-11 07:30:00","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":288871,"visible":true,"origin":"","legend":"\u003cp\u003eMann-Whitney test showed no statistically significant difference at baseline between diet and medication. Wilcoxon test was used to compare mean biomarker levels before and after treatment. V2: visit 2, after 8 weeks of treatment. P\u0026lt;0.05 was used.\u003c/p\u003e","description":"","filename":"floatimage44.png","url":"https://assets-eu.researchsquare.com/files/rs-6138161/v1/3bf5dc401edce28301a8e6aa.png"},{"id":99172895,"identity":"6af96838-8e0c-4249-a20e-449197bc6e48","added_by":"auto","created_at":"2025-12-29 16:11:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1317817,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6138161/v1/86afabb3-e044-457c-9328-47dbc52fd81c.pdf"},{"id":78230784,"identity":"8af0fe3b-4570-4265-ab79-55baa2413ff1","added_by":"auto","created_at":"2025-03-11 07:30:05","extension":"doc","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":76800,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfiguresconsortdiagramanddemographic.doc","url":"https://assets-eu.researchsquare.com/files/rs-6138161/v1/fa5fa7dda6cd567dd1ef226c.doc"}],"financialInterests":"Competing interest reported. JT has given Scientific advice to AlfaWassermann, Allergan, Christian Hansen, Danone, Grünenthal, Ironwood, Janssen, Kiowa Kirin, Menarini, Mylan, Neutec, Novartis, Noventure, Nutricia, Shionogi, Shire, Takeda, Theravance, Tramedico, Truvion, Tsumura, Zealand and Zeria pharmaceuticals, has received research support from Shire, Sofar and Tsumura, and has served on the Speaker bureau for Abbott, Allergan, AstraZeneca, Janssen, Kyowa Kirin, Menarini, Mylan, Novartis, Shire, Takeda, Truvion and Zeria. Funding was provided by a Methusalem grant from Leuven University to JT\nThis study was supported by a research grant from the Belgian Health Care Knowledge Centre (KCE).\nQuestionnaires in this trial were provided by the Rome Foundation research Institute.","formattedTitle":"Inflammatory biomarkers in newly diagnosed primary care Irritable Bowel Syndrome: a subanalysis of the DOMINO Randomized Trial","fulltext":[{"header":"Background","content":"\u003cp\u003eIrritable bowel syndrome (IBS) is one of the most common functional gastro-intestinal disorders, or disorders of gut-brain interaction (DBGIs). According to Rome IV criteria, IBS is defined by recurrent abdominal pain for at least 1 day per week in the last 3 months in the absence of organic causes and associated by two of the following criteria: related to defecation and/or associated with a change in frequency and/or appearance of stool (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). The Rome IV global epidemiology study showed a worldwide IBS prevalence of 4.1% based on the internet survey (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). A representative survey in 1012 adults of the Belgian population showed a Rome IV based prevalence of 5.5% rising to 17.6% for self-reported IBS according to a general descriptive definition (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). Patients can be subdivided according to their dominant stool pattern into IBS-diarrhea (IBS-D), IBS-constipation (IBS-C), IBS-mixed (IBS-M) and IBS-unclassified (IBS-U)(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Several pathophysiological mechanisms have been implicated in IBS pathogenesis, including altered colonic motility, visceral hypersensitivity, increased mucosal permeability, imbalance of gut microbiota (dysbiosis), as well as psychological factors (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Most recently the focus has been on low-grade inflammation in the colonic mucosa, especially in IBS-D (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHowever, it is often difficult to differentiate IBS from other gastrointestinal disorders. Fecal calprotectin (FC) is a non-invasive inflammatory marker commonly used for distinguishing inflammatory bowel disease (IBD) from IBS (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Since low-grade inflammation has been implicated in the pathophysiology of IBS, a subgroup of IBS may present with increased FC levels (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Fecal human \u0026szlig;-Defensin-2 (HBD-2) has also been shown to be significantly elevated in IBS compared to ulcerated colitis, but little is known about the correlation between HBD-2 and IBS (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). In addition, several studies have reported an increase in B lymphocyte activation and by extension immunoglobulin production in IBS (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). However, mucosal B cells that are responsible for secretory immunoglobulin A (sIgA) secretion, which is important for gut mucosa protection from food antigens and pathogens, have been shown to be reduced in IBS, suggesting an altered enteral immune defense (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). Still, it remains unclear whether there is a causal relationship between reduced sIgA production and bowel symptoms (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). In addition, according to a previous UK study, 6.1% of IBS-D patients had pancreatic exocrine insufficiency defined by fecal pancreas elastase-1 (Fel-1) levels lower than 100 \u0026micro;g /g (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDietary and lifestyle changes in combination with symptom-based pharmacological treatment is considered as first-line treatment for IBS (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). In Europe, musculotropic spasmolytics are frequently prescribed and considered standard medical therapy (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Otilonium bromide (OB), a L-type calcium channel blocker improves bloating and abdominal pain compared to placebo, with a significant response already occurring after 4 weeks of treatment (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e).The role of dietary treatment is increasing in IBS, as the majority of the patients are reporting food as a trigger for their symptoms. A diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) improves IBS symptoms after 6\u0026ndash;8 weeks. Unfortunately, due to the complexity and the requirement of a professional dietitian this is often dismissed in primary care (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). In the DOMINO trial, a self-management smartphone application was evaluated (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). This pragmatic randomized open-label parallel designed trial showed that the DOMINO application, a FODMAP-lowering diet, was superior to a spasmolytic agent (OB) in improving symptoms in a large cohort of primary care IBS patients (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). As such, a FODMAP lowering diet should be considered as a first-line treatment in primary care IBS (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Studies showed that the low FODMAP diet reduces the levels of pro-inflammatory interleukins, fecal bacteria, total short chain fatty acids and N-butyric acid (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). Therefore, this diet might be able to diminish the low-grade inflammation and subsequently inflammatory biomarkers in some patients. In addition, some literature suggests antimicrobial actions of OB, and a potential to change gut microbiota load and composition could be associated with altered low-grade inflammation (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). Because of the suggested low-grade inflammation in IBS pathology, our aim was to explore the levels of several inflammatory markers in recently diagnosed primary care IBS patients. In addition, we aimed to investigate the potential utility of those biomarkers in the diagnosis and prediction of treatment response in this cohort.\u003c/p\u003e "},{"header":"Methods","content":"\u003ch2\u003eStudy design\u003c/h2\u003e\u003cp\u003eCurrent study builds upon the DOMINO trial, which is an open, pragmatic randomized parallel-group design study in which 472 Belgian primary care IBS patients were randomized between July 2018 and December 2019 (1:1 ratio) to 8 weeks of treatment with OB 40mg or a FODMAP lowering diet through a mobile smartphone application (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e)(Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Eligible patients were newly treated IBS patients. The trial was registered with ClinicalTrials.gov (NCT04270487, registered on 2020-05-04).\u003c/p\u003e \u003cp\u003eThe diagnosis was made by primary care physicians (PCPs, n\u0026thinsp;=\u0026thinsp;105). At the screening visit (visit 0) informed consent was obtained prior to any study procedures (S59482, clinicaltrial.gov). At baseline, information on patient\u0026rsquo;s demographics and IBS stool type was collected. Patients were subdivided based on their dominant stool type into IBS-D, IBS-C, IBS-M and IBS-U as defined by the clinical opinion of the PCP. Within 14 days after visit 0, patients were randomized to either OB or the smartphone application.\u003c/p\u003e \u003cp\u003ePatients completed questionnaires at baseline, 4 weeks, and 8 weeks to score their symptoms. The consent for collection of biological samples was optional for the patients. Stool and blood samples were collected at the baseline visit (visit 1) and at the end of the 8-week treatment period (visit 2) for the analysis of inflammatory markers.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eQuestionnaires\u003c/h2\u003e \u003cp\u003eThroughout the study, patients completed the Rome IV IBS diagnostic questionnaire to characterize patients fulfilling Rome IV criteria for IBS (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). If conform to the criteria, they are referred to as Rome +.\u003c/p\u003e \u003cp\u003eIn addition, patients completed the IBS symptom severity scale (IBS-SSS) to asses symptom severity and treatment response (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). IBS-SSS was completed at baseline (visit 1) and after 4 and 8 weeks of treatment. Patients were subdivided based on their symptom severity score: normal: \u0026lt;75; mild: [75\u0026ndash;175], moderate [175\u0026ndash;300], severe\u0026thinsp;\u0026gt;\u0026thinsp;300 with a maximum achievable score of 500 (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). A responder to the allocated treatment was defined as a patient with an improvement of 50 points or more on the IBS-SSS at the end of the treatment period compared to baseline (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eInflammatory markers\u003c/h3\u003e\n\u003cp\u003eAll biological samples were processed by the medical laboratory CRI (Zwijnaarde, Belgium). Stool samples were analyzed to score fecal calprotectin (FC) levels (preparation by EliA Stool Extraction kit 2, ThermoFisher Scientific; ref 14-5651-01), secretory IgA (sIgA) (ELISA, thunderbolt), Beta-defensin 2 (HBD-2) (ELISA, thunderbolt), Fecal elastase (Fel-1) (ELISA, thunderbolt). C-reactive protein (CRP) (CRPL3 kit, following Roche, ref. 05172373190 instruction, Cobas 800 c702) was defined by analyzing blood samples.\u003c/p\u003e \u003cp\u003eThe biological thresholds for these markers were defined as followed: FC (\u0026gt;\u0026thinsp;100 \u0026micro;g /g), sIgA (\u0026gt;\u0026thinsp;5000 \u0026micro;g/ml), HBD-2 (\u0026gt;\u0026thinsp;60 ng/ml), CRP (\u0026gt;\u0026thinsp;5 mg/L) and for pancreatic exocrine insufficiency by pancreatic elastase (mild 200\u0026ndash;500, moderate 100\u0026ndash;200, severe\u0026thinsp;\u0026lt;\u0026thinsp;100\u0026micro;g/g).\u003c/p\u003e \u003cp\u003eWhen lab values were reported outside the measurable range by CRI laboratory (CRP\u0026thinsp;\u0026lt;\u0026thinsp;0.3, sIgA\u0026thinsp;\u0026lt;\u0026thinsp;278 or \u0026gt;\u0026thinsp;7500, HBD-2\u0026thinsp;\u0026lt;\u0026thinsp;20 and fel-1\u0026thinsp;\u0026lt;\u0026thinsp;50 or \u0026gt;\u0026thinsp;500) by CRI using \u0026ldquo;\u0026lt;\u0026rdquo; or \u0026ldquo;\u0026gt;\u0026rdquo; sign, we assumed the value to be \u0026plusmn;\u0026thinsp;0.1 for CRP, sIgA, HBD-2 and Fel-1.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eData were analyzed using Graphpad Prism version 8.4.3 for OS X, GraphPad Software, La Jolla California USA, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ewww.graphpad.com\u003c/a\u003e\u003c/span\u003e\u003cspan address=\"http://www.graphpad.com\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. The significance threshold was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. Data are shown as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SEM. Mann-whitney-U test, Wilcoxon test, Spearman correlation, Kruskal Wallis test and Chi-square analysis were used for evaluating the clinical relevance and correlation of the biomarkers with patient\u0026rsquo;s demographics, symptom severity, IBS subtype, Rome IV and treatment response.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003ePatient population and baseline characteristics\u003c/h2\u003e \u003cp\u003e459 patients were randomized, both groups were well matched (supplementary table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In this study cohort, 94% (n\u0026thinsp;=\u0026thinsp;445) of patients gave consent to provide blood and stool samples. Of the 445 patients (74.6% female, 41.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7 years, BMI 24.58\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5, mean IBS-SSS 265.5\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6), 70% fulfilled the strict Rome IV criteria for IBS and are referred to as Rome +. The other patients had IBS according to the clinician\u0026rsquo;s opinion (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e), but did not fulfill Rome criteria and are referred to as Rome -. Flow of participants and samples shown in supplementary Fig.\u0026nbsp;1.\u003c/p\u003e \u003cp\u003eIn the entire cohort, inflammatory marker levels were on average below biological thresholds (Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Nonetheless, abnormal baseline levels were observed for FC, CRP, sIgA, and HBD-2 in 9%, 19%, 15% and 20% of the patients respectively. Only 2% of the patients showed fel-1 levels suggestive of pancreatic insufficiency when applying the predefined cut-off level.\u003c/p\u003e \u003cp\u003eIBS-SSS at baseline was not associated with the levels of CRP (r=-0.007, p\u0026thinsp;=\u0026thinsp;0.86), FC (r=-0.004, p\u0026thinsp;=\u0026thinsp;0.99), sIgA (r\u0026thinsp;=\u0026thinsp;0.03, p\u0026thinsp;=\u0026thinsp;0.59) and HBD-2 (r=-0.074, p\u0026thinsp;=\u0026thinsp;0.13). However, a significant correlation was found between BMI and CRP (r\u0026thinsp;=\u0026thinsp;0.29, p\u0026thinsp;=\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and FC (r\u0026thinsp;=\u0026thinsp;0.11,p\u0026thinsp;=\u0026thinsp;0.02), but not for HBD-2 (r=-0.02,p\u0026thinsp;=\u0026thinsp;0.74), and sIgA (r\u0026thinsp;=\u0026thinsp;0.02,p\u0026thinsp;=\u0026thinsp;0.64).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eRome IV subgroups\u003c/h2\u003e \u003cp\u003eThere was no significant difference in mean biomarker values between Rome\u0026thinsp;+\u0026thinsp;and Rome -, except for Fel-1 (Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMean levels of biomarker and Mann-Whithey-U test between Rome IV\u0026thinsp;+\u0026thinsp;and Rome IV-\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAll patients\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;445)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRome IV +\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;308)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRome IV \u0026ndash;\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;129)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003cp\u003e(Rome IV\u0026thinsp;+\u0026thinsp;vs. Rome IV -)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCRP (mg/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e3.09\u0026thinsp;\u0026plusmn;\u0026thinsp;9.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e3.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFC (mg/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e57.71\u0026thinsp;\u0026plusmn;\u0026thinsp;10.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e67.28\u0026thinsp;\u0026plusmn;\u0026thinsp;15.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.74\u0026thinsp;\u0026plusmn;\u0026thinsp;6.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003esIgA (\u0026micro;g/ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e2415\u0026thinsp;\u0026plusmn;\u0026thinsp;107.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e2497\u0026thinsp;\u0026plusmn;\u0026thinsp;134.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2225\u0026thinsp;\u0026plusmn;\u0026thinsp;182.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHBD-2 (ng/ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e48.86\u0026thinsp;\u0026plusmn;\u0026thinsp;3.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e46.06\u0026thinsp;\u0026plusmn;\u0026thinsp;3.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e56.73\u0026thinsp;\u0026plusmn;\u0026thinsp;7.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFel-1 (\u0026micro;g/g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e397.8\u0026thinsp;\u0026plusmn;\u0026thinsp;5.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e402.80\u0026thinsp;\u0026plusmn;\u0026thinsp;6.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e383.0\u0026thinsp;\u0026plusmn;\u0026thinsp;9.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.03\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIBS-SSS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e265.5\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e293.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e199.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStool pattern\u003c/h3\u003e\n\u003cp\u003ePatients were divided according to their dominant stool type as follows 20% IBS-C, 28% IBS-D, 40% IBS-M and 12% IBS-U. IBS-C patients were characterized by a significantly higher IBS-SSS compared to other subtypes (Table\u0026nbsp;2). However, there was no significant difference in baseline biomarker levels found between all subtypes, except for CRP, which was significantly lower in IBS-C compared to all other subtypes (table 2). In addition, Chi-square testing showed that there is no significant relationship between the stool pattern subtype and the presence of abnormal CRP (χ\u0026sup2; (3, N\u0026thinsp;=\u0026thinsp;433)\u0026thinsp;=\u0026thinsp;7.03, p\u0026thinsp;=\u0026thinsp;0.07), FC (χ\u0026sup2; (3, N\u0026thinsp;=\u0026thinsp;436)\u0026thinsp;=\u0026thinsp;0.26, p\u0026thinsp;=\u0026thinsp;0.97), HBD-2 (χ\u0026sup2; (3, N\u0026thinsp;=\u0026thinsp;436)\u0026thinsp;=\u0026thinsp;2.09, p\u0026thinsp;=\u0026thinsp;0.56) and sIgA (χ\u0026sup2; (3, N\u0026thinsp;=\u0026thinsp;436)\u0026thinsp;=\u0026thinsp;1,123, p\u0026thinsp;=\u0026thinsp;0.77). (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTable 2. Biomarker levels in all IBS subtypes\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIBS-C\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;90)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIBS-D\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;123)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eIBS-M\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;177)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIBS-U\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;55)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP value \u0026dagger;\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCRP (mg/L)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e3.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e3.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e3.26\u0026thinsp;\u0026plusmn;\u0026thinsp;1.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.007\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFC (mg/kg)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e53.55\u0026thinsp;\u0026plusmn;\u0026thinsp;19.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e75.92\u0026thinsp;\u0026plusmn;\u0026thinsp;28.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e55.47\u0026thinsp;\u0026plusmn;\u0026thinsp;15.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e31.24\u0026thinsp;\u0026plusmn;\u0026thinsp;5.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003esIgA (\u0026micro;g/ml)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e2596\u0026thinsp;\u0026plusmn;\u0026thinsp;267.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e2517\u0026thinsp;\u0026plusmn;\u0026thinsp;200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e2304\u0026thinsp;\u0026plusmn;\u0026thinsp;161\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e2250\u0026thinsp;\u0026plusmn;\u0026thinsp;315.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHBD-2 (ng/ml)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e53.99\u0026thinsp;\u0026plusmn;\u0026thinsp;7.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e51.11\u0026thinsp;\u0026plusmn;\u0026thinsp;8.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e46.75\u0026thinsp;\u0026plusmn;\u0026thinsp;4.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e42.30\u0026thinsp;\u0026plusmn;\u0026thinsp;6.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIBS-SSS \u0026sect;\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e284.7\u0026thinsp;\u0026plusmn;\u0026thinsp;9.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e263.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e267.5\u0026thinsp;\u0026plusmn;\u0026thinsp;7.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e231.8\u0026thinsp;\u0026plusmn;\u0026thinsp;13.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.04\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e\u0026plusmn; values are means\u0026thinsp;\u0026plusmn;\u0026thinsp;SEM \u0026sect; Symptom severity was assessed using the IBS symptom severity scale (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). \u0026dagger; P values are shown from Kruskal-Wallis tests comparing the four IBS stool pattern subtypes. Bold is significant.\u003c/p\u003e \n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eEvaluation of treatment effect\u003c/h2\u003e \u003cp\u003eIn both the FODMAP-lowering diet application (n\u0026thinsp;=\u0026thinsp;218) and OB (n\u0026thinsp;=\u0026thinsp;227) arm, Mann-whitney test showed no significant difference between responders and non-responders at baseline (CRP (OB: p\u0026thinsp;=\u0026thinsp;0.84, Diet p\u0026thinsp;=\u0026thinsp;0.6), FC (OB: p\u0026thinsp;=\u0026thinsp;0.70,Diet p\u0026thinsp;=\u0026thinsp;0.20), sIgA (OB: p 0.55, Diet p\u0026thinsp;=\u0026thinsp;0.82) and HBD-2 (OB: p\u0026thinsp;=\u0026thinsp;0.19, Diet p\u0026thinsp;=\u0026thinsp;0.43) (Fig.\u0026nbsp;3). After 8 weeks of treatment, stool markers FC, sIgA, and HBD-2 decreased in both study groups (Fig.\u0026nbsp;4). However, this trend was only significant for HBD-2 in both diet and OB, and for FC in the diet group (Fig.\u0026nbsp;4). As for the blood sample, CRP did decrease numerically in the diet group, but this change was not statistically significant (Fig.\u0026nbsp;4).\u003c/p\u003e \u003cp\u003eIn addition, for diet and OB no significant correlation was observed between the change in IBS-SSS (%) and changes in biomarker levels in both responders and non-responders. There was also no significant correlation between the change in FC and HBD between responders and non-responders in both arms. However, we found a small, but significant correlation between the change in FC and CRP in the responder group for medication (r\u0026thinsp;=\u0026thinsp;0.24, p\u0026thinsp;=\u0026thinsp;0.009), but not for diet (r\u0026thinsp;=\u0026thinsp;0.15, p\u0026thinsp;=\u0026thinsp;0.08).\u003c/p\u003e \u003cp\u003eIBS-SSS at the end of the treatment period (visit 2) was not associated with the levels of CRP (r=-0.049, p\u0026thinsp;=\u0026thinsp;0.34), FC (r\u0026thinsp;=\u0026thinsp;0-0.04, p\u0026thinsp;=\u0026thinsp;0.43), sIgA (r=-0.005, p\u0026thinsp;=\u0026thinsp;0.92) and HBD-2 (r=-0.009, p\u0026thinsp;=\u0026thinsp;0.86).\u003c/p\u003e "},{"header":"Discussion","content":"\u003cp\u003eTo investigate the role of low-grade inflammation in the pathophysiology of IBS, we examined the levels of various biomarkers in biological samples from 445 primary care IBS patients of the DOMINO study (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). The DOMINO study has previously shown that IBS patients symptoms improve after 8-weeks treatment with a spasmolytic agent (OB) and a FODMAP lowering diet provided to patients though a mobile application. Moreover, IBS patients showed a significantly higher clinical response to the diet compared to the OB study arm (71% (155/218) vs 61% (133/217), p\u0026thinsp;=\u0026thinsp;0.03). During this study, blood and stool samples of patients were collected at baseline and after treatment. In the current manuscript, we describe the levels of FC, sIgA, HBD-2, and Fel-1 in stool samples, and CRP in serum. We compared biological markers at baseline to standard biological thresholds and we explored plausible impact of the allocated treatment.\u003c/p\u003e \u003cp\u003eOur study did not find a significant correlation between IBS symptom severity scores and biomarker levels in patients at baseline. We found that CRP levels were associated with BMI in our patients, which most likely reflects the known link between metabolic syndrome and inflammation(\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). Studies of the effect of obesity on symptom severity in IBS are ambivalent, further research is needed to evaluate a possible relation(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e) Both treatments did not affect the levels of CRP after 8 weeks. Several studies reported an elevated hs-CRP in IBS compared to healthy controls (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). However, only 19% showed abnormal CRP levels at baseline in our study population, thus failing to indicate significant systemic inflammation.\u003c/p\u003e \u003cp\u003eWe assessed the presence of pancreatic insufficiency by measuring Fel-1 levels and found that only 2% of the cohort had aberrant levels. While a previous study suggested considering pancreatic insufficiency in IBS-D patients, we did not observe any differences between the different IBS subtypes(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn our cohort, 9% of IBS patients had abnormal FC levels, which is lower than what has been reported in previous studies using the same cut-off level(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). This highlights the importance of further investigations, such as endoscopy, to avoid misdiagnosis of IBS as inflammatory bowel disease (IBD). However, due to the pragmatic set-up of this study, further clinical investigations of the patients were not performed. HBD-2 and sIgA levels were elevated in a respectively 20 and 15% of all patients, but the literature on the relationship between these biomarkers and IBS is limited. The levels of these were not correlated with symptom severity or stool subtype in our cohort. A small study of Langhorst et al. showed elevated HBD-2 levels similar to active colitis ulcerosa patients(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Thus suggesting an activation of the mucosal innate immune system as a driver of a proinflammatory response(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe lowering FODMAP diet and OB treatments led to a decrease in biomarker levels, with HBD-2 being significantly lower in both groups and FC being reduced in the diet group. Based on the literature we can hypothesize that the observed changes in inflammatory markers may be linked to known effects on permeability in the dietary intervention, which has previously been shown for a gluten-free diet in IBS and for a low FODMAP diet in FD (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e). The study of Prospero et al. also demonstrated an improvement of gut permeability after a low FODMAP diet in IBS patients by measuring markers of function/integrity of the intestinal barrier (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). Previous research has also shown that increased gut permeability can contribute to inflammation(\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFurther research is warranted to further explore the role of the intestinal barrier as a treatment target. Another possibility is that the higher inflammation prior to treatment could be the consequence of seeking medical attention at the time of concurrent gastrointestinal infection leading to the subsequent diagnosis of IBS.\u003c/p\u003e \u003cp\u003eOur study is not without limitations.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ePost hoc analysis and not the primary endpoin, but a large number of samples.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePragmatic study, primary care IBS, no close follow up to adherence to the diet and OB intake.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e8 week follow up, so long term effect is not known.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNot all patients enrolled in this study fulfilled the Rome IV criteria\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eFor clinical practice it is not recommended to standard evaluation of all these biological markers. The aim of this study is mainly exploratory for the further understanding of IBS. Guidelines do recommend standard blood work with full blood count, sedimentation rate, CRP and coeliac serology as well as FC (the latter in the presence of diarrhea in a patient under 45 years of age)(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). In absence of alarm symptoms and if those tests are normal, asking for further investigations should be limited and left to the physician\u0026rsquo;s informed judgment(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). The Rome IV criteria applicability in primary care is being questioned, since overly rigid criteria can delay diagnosis in those patients and those criteria where primary based on secondary care patients(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eTo summarize our findings, our data suggests that broad use of inflammatory biomarkers to assess symptom severity in primary care IBS patients is not recommended. Additionally, we observed a reduction in the levels of all inflammatory biomarkers in response to both treatments. Further research will be needed to establish whether this represents an anti-inflammatory effect of the dietary intervention or OB treatment, or is a bystander effect reflecting some concurrent infection that prompted patients to seek medical attention.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eDBGIs \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Disorders of Gut-brain interaction\u003c/p\u003e\n\u003cp\u003eFC \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Fecal calprotectin\u003c/p\u003e\n\u003cp\u003eFel-1 \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Fecal pancreas elastase 1\u003c/p\u003e\n\u003cp\u003eFODMAP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Fermentable oligosaccharides, disaccharides, monoasaccharides and \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; polyols\u003c/p\u003e\n\u003cp\u003eHBD-2 \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Human B-defensin-2\u003c/p\u003e\n\u003cp\u003eIBS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Irritable Bowel Syndrome\u003c/p\u003e\n\u003cp\u003eIBS-C \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; IBS constipation subtype\u003c/p\u003e\n\u003cp\u003eIBS-D \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;IBS diarrhea subtype\u003c/p\u003e\n\u003cp\u003eIBS-SSS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;IBS symptom severity scale\u003c/p\u003e\n\u003cp\u003eIBS-M \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;IBS mixed subtype\u003c/p\u003e\n\u003cp\u003eIBS-U \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; IBS Unclassified subtype\u003c/p\u003e\n\u003cp\u003eOB \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Otilonium bromide\u003c/p\u003e\n\u003cp\u003ePCP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Primary care physician\u003c/p\u003e\n\u003cp\u003esIgA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;secretory Immunoglobulin A\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJT has given Scientific advice to AlfaWassermann, Allergan, Christian Hansen, Danone, Gr\u0026uuml;nenthal, Ironwood, Janssen, Kiowa Kirin, Menarini, Mylan, Neutec, Novartis, Noventure, Nutricia, Shionogi, Shire, Takeda, Theravance, Tramedico, Truvion, Tsumura, Zealand and Zeria pharmaceuticals, has received research support from Shire, Sofar and Tsumura, and has served on the Speaker bureau for Abbott, Allergan, AstraZeneca, Janssen, Kyowa Kirin, Menarini, Mylan, Novartis, Shire, Takeda, Truvion and Zeria. Funding was provided by a Methusalem grant from Leuven University to JT\u003c/p\u003e\n\u003cp\u003eThis study was supported by a research grant from the Belgian Health Care Knowledge Centre (KCE).\u003c/p\u003e\n\u003cp\u003eQuestionnaires in this trial were provided by the Rome Foundation research Institute.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe DOMINO Study was funded through the Belgian Health Care Knowledge Centre (KCE) Trials Program (study ID KCE16001), a national public funding program of non-commercial trials. KCE provided feedback on the design and conduct of the study but was not involved in the collection, management, analysis, or interpretation of the data. KCE provided comments on the drafted clinical study report and the manuscript for publication, but no publication restrictions apply.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the Belgian Health Care Knowledge Centre, in collaboration with Nelle Stocquart and Hilde Nevens and by the Rome Foundation Research Institute.\u003c/p\u003e\n\u003cp\u003eKaren Van den Houte is supported by a PDM funding obtained by the Internal Funds KU Leuven.\u003c/p\u003e\n\u003cp\u003eThis study was conducted in collaboration with\u0026nbsp;\u003cbr\u003e\u0026nbsp;Cerba Healthcare Belgium \u0026ndash; Labo CRI, Zwijnaarde, Belgium for the collection and analysis of biological samples.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eStool analysis were conducted in collaboration with Rega Institute, KULeuven, Belgium and Mylan, Belgium.\u003c/p\u003e\n\u003cp\u003eThe DOMINO application was developed by EverywhereIM (Amsterdam, The Netherlands).\u003c/p\u003e\n\u003cp\u003eWe would like to thank and acknowledge the 105 Belgian primary care physicians for their good performance and commitment in this trial as well as the 472 participating patients. The list of recruited study investigators is attached in the addendum.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study involves human participants and was approved by the Ethical Committee Research UZ/KU Leuven (S59482). Participants gave informed consent to participate in the study before taking part.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStudy conception and design : FC and \u0026nbsp;JT; Data collection: CT, KVdH, LB, FC, JT, LC, SC, OG, SM, CP, WR, JS, JR, RVB, OV, SVS and BG; Analysis and interpretation of results: CT, KVdH, FC, JR, BG and JT; Draft manuscript: CT, KVdH, FC and JT. All authors reviewed the results and approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMearin F, Lacy BE, Chang L, Chey WD, Lembo AJ, Simren M et al. Bowel Disorders Gastroenterol. 2016.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSperber AD, Bangdiwala SI, Drossman DA, Ghoshal UC, Simren M, Tack J, et al. Worldwide Prevalence and Burden of Functional Gastrointestinal Disorders, Results of Rome Foundation Global Study. Gastroenterology. 2021;160(1):99\u0026ndash;e1143.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan den Houte K, Carbone F, Pannemans J, Corsetti M, Fischler B, Piessevaux H, et al. Prevalence and impact of self-reported irritable bowel symptoms in the general population. United Eur Gastroenterol J. 2019;7(2):307\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBennet SM, Ohman L, Simren M. Gut microbiota as potential orchestrators of irritable bowel syndrome. Gut Liver. 2015;9(3):318\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCorsetti M, Van Oudenhove L, Tack J. The quest for biomarkers in IBS-where should it lead us? Neurogastroenterol Motil. 2014;26(12):1669\u0026ndash;76.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHoltmann GJ, Ford AC, Talley NJ. Pathophysiology of irritable bowel syndrome. Lancet Gastroenterol Hepatol. 2016;1(2):133\u0026ndash;46.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMumolo MG, Bertani L, Ceccarelli L, Laino G, Di Fluri G, Albano E, et al. From bench to bedside: Fecal calprotectin in inflammatory bowel diseases clinical setting. World J Gastroenterol. 2018;24(33):3681\u0026ndash;94.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRogler G, Aldeguer X, Kruis W, Lasson A, Mittmann U, Nally K, et al. Concept for a rapid point-of-care calprotectin diagnostic test for diagnosis and disease activity monitoring in patients with inflammatory bowel disease: expert clinical opinion. J Crohns Colitis. 2013;7(8):670\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMari A, Baker FA, Mahamid M, Yacoob A, Sbeit W, Khoury T. Clinical utility of fecal calprotectin: potential applications beyond inflammatory bowel disease for the primary care physician. Ann Gastroenterol. 2019;32(5):425\u0026ndash;30.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLanghorst J, Junge A, Rueffer A, Wehkamp J, Foell D, Michalsen A, et al. Elevated human beta-defensin-2 levels indicate an activation of the innate immune system in patients with irritable bowel syndrome. Am J Gastroenterol. 2009;104(2):404\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOhman L, Simr\u0026eacute;n M. Pathogenesis of IBS: role of inflammation, immunity and neuroimmune interactions. Nat Rev Gastroenterol Hepatol. 2010;7(3):163\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eForshammar J, Isaksson S, Strid H, Stotzer PO, Sj\u0026ouml;vall H, Simr\u0026eacute;n M, et al. A pilot study of colonic B cell pattern in irritable bowel syndrome. Scand J Gastroenterol. 2008;43(12):1461\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeeds JS, Hopper AD, Sidhu R, Simmonette A, Azadbakht N, Hoggard N, et al. Some patients with irritable bowel syndrome may have exocrine pancreatic insufficiency. Clin Gastroenterol Hepatol. 2010;8(5):433\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlgera J, Colomier E, Simr\u0026eacute;n M. The Dietary Management of Patients with Irritable Bowel Syndrome: A Narrative Review of the Existing and Emerging Evidence. 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Gut. 2021;70(7):1214\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-gastroenterology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmge","sideBox":"Learn more about [BMC Gastroenterology](http://bmcgastroenterol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmge/default.aspx","title":"BMC Gastroenterology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"IBS, DOMINO trial, FODMAP, otilonium bromide, inflammatory markers","lastPublishedDoi":"10.21203/rs.3.rs-6138161/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6138161/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThe role of low-grade-inflammation in Irritable Bowel Syndrome (IBS) a common disorder of gut-brain interaction is unclear. Association with symptom severity, as well as effects of first line treatments are understudied. In a large cohort of primary care IBS patients (DOMINO trial), a FODMAP-lowering diet application was superior in improving symptoms compared to standard medical therapy (otilonium bromide, OB). We investigated the level of pro-inflammatory markers in this IBS cohort and its changes by the DOMINO application and OB.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eInflammatory markers fecal calprotectin (FC), secretory IgA (sIgA), beta-defensin 2 (HBD-2), fecal elastase (Fel-1), and C-reactive protein (CRP) were analyzed at baseline and after 8-week of treatment (diet or medication). In addition, patients filled out questionnaires to score IBS criteria (Rome IV), IBS subtypes, and symptom severity (IBS-SSS). We used Mann-Whitney-U test, Wilcoxon test, Spearman correlation, Kruskal Wallis test and Chi-square analysis to analyze our data.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eIn the DOMINO trial, stool and blood samples of 445 patients were collected before and after treatment. At baseline, respectively 9, 19, 15, 20, 2% of the patients showed abnormal levels of CRP, FC, sIgA, HBD-2, and Fel-1 compared to standard thresholds. However, these markers did not correlate with IBS-SSS. In addition, CRP was significantly lower in IBS-C patients compared to other IBS subtypes. After a 8-week treatment with a FODMAP lowering diet application, both HBD-2 and FC were significantly decreased, while only HBD-2 was decreased with OB.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eInflammatory markers (FC, CRP, sIgA, HBD-2, Fel-1) were not correlated with symptom severity in a large primary care IBS cohort. All markers decreased after 8-week treatment, with significant differences for HBD-2 and FC. The anti-inflammatory effect of both treatments needs to be further investigated. \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eTrial registration\u003c/span\u003e: The trial was registered with ClinicalTrials.gov (NCT04270487, registered on 2020-05-04).\u003c/p\u003e","manuscriptTitle":"Inflammatory biomarkers in newly diagnosed primary care Irritable Bowel Syndrome: a subanalysis of the DOMINO Randomized Trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-11 07:21:55","doi":"10.21203/rs.3.rs-6138161/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-03-07T11:52:19+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-06T09:53:45+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-06T09:51:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Gastroenterology","date":"2025-03-02T08:12:57+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-gastroenterology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmge","sideBox":"Learn more about [BMC Gastroenterology](http://bmcgastroenterol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmge/default.aspx","title":"BMC Gastroenterology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cea1272b-fa6d-4994-a568-20d82a498824","owner":[],"postedDate":"March 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-29T16:09:52+00:00","versionOfRecord":{"articleIdentity":"rs-6138161","link":"https://doi.org/10.1186/s12876-025-04494-7","journal":{"identity":"bmc-gastroenterology","isVorOnly":false,"title":"BMC Gastroenterology"},"publishedOn":"2025-12-23 15:57:53","publishedOnDateReadable":"December 23rd, 2025"},"versionCreatedAt":"2025-03-11 07:21:55","video":"","vorDoi":"10.1186/s12876-025-04494-7","vorDoiUrl":"https://doi.org/10.1186/s12876-025-04494-7","workflowStages":[]},"version":"v1","identity":"rs-6138161","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6138161","identity":"rs-6138161","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}