{"paper_id":"26d98bc3-2af0-4a99-912c-cfde9d0befab","body_text":"Extended hydrogen breath test analysis for optimized diagnosis of SIBO-positive IBS patients | 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 Extended hydrogen breath test analysis for optimized diagnosis of SIBO-positive IBS patients Atti-La Dahlgren, Per Grybäck, Hans Jacobsson, Per M Hellström This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8800553/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Apr, 2026 Read the published version in BMC Gastroenterology → Version 1 posted 11 You are reading this latest preprint version Abstract Background: Small intestinal bacterial overgrowth (SIBO) is suggested in irritable bowel syndrome (IBS). Optimal hydrogen levels and time frame for diagnosing SIBO are still under discussion. Our primary aim was to consolidate a discriminating threshold for a positive lactulose hydrogen breath test (LHBT) in IBS. As a secondary aim, we optimized the diagnostic time frame for the small bowel. Methods: LHBT was performed on 503 subjects who met the inclusion criteria. After excluding non-hydrogen producers, the remaining 462 subjects were 92 healthy individuals and 370 IBS patients. Peak hydrogen levels were compared as mean values with 95% confidence intervals. Results: At the 80-min orocecal cutoff , healthy subjects showed a peak hydrogen of 10(9–12) ppm compared with 20(18–23) ppm in the overall IBS group (p <0.0001). Using ≥20 ppm cutoff , sensitivity was 38% and specificity 77%. Peak hydrogen was highest in IBS-D (30(26-33) ppm; p <0.0001), intermediate in IBS-M (14(11-17) ppm), and lowest in IBS-C (10(7-13) ppm), showing sensitivities of 61%, 23%, and 10%, respectively, with specificity 77%. After antibiotics, IBS patients with low hydrogen were unchanged, whereas most with high hydrogen reduced their hydrogen levels (p <0.01). Conclusion: Using a cutoff level of 20 ppm during the first 80 minutes, LHBT can diagnose SIBO in people with IBS showing high breath hydrogen, as compared with those having low breath hydrogen. Hence, SIBO-positive patients can be separated from SIBO-negative IBS patients. To this end, a majority of SIBO-positive subjects respond to antibiotic treatment. Hydrogen IBS Lactulose Microbiota Small intestinal bacterial overgrowth SIBO Figures Figure 1 Figure 2 Figure 3 Figure 4 INTRODUCTION Accumulating evidence suggests a potential role for dysbiosis in irritable bowel syndrome (IBS) ( 1 – 3 ). Small intestinal bacterial overgrowth (SIBO) is detected in up to 78% of IBS cases ( 4 ). This sizable prevalence may be attributed to differences in ethnicity, microbiology, and various diagnostic criteria employed. Non-invasive breath tests have gained interest due to the ease and timeliness with which an SIBO diagnosis can be made. Still, bacterial cultures of aspirate from the proximal jejunum are described as the gold standard for diagnosing SIBO ( 5 ). However, this has been challenged because it carries a risk of sampling error if not multiple regions of the small bowel are sampled, and the cut-off level for SIBO has been discussed ( 6 , 7 ). In addition, there is a major contamination risk at sampling, and commonly the sampled bacteria are not culturable; therefore, this diagnostic method is suboptimal ( 5 ). Different types of breath tests have been employed but are hampered by the lack of a true standard for the performance and interpretation of data. Depending on the chosen fermentable bacterial substrate and the timing of readouts and diagnostic hydrogen cut-off levels, various studies arrive at different recommendations for diagnosing SIBO. This has led to interactive working groups advocating essential rules for employing hydrogen breath tests for diagnostic purposes ( 8 – 10 ). The lactulose hydrogen breath test (LHBT) is clinically used as a non-invasive proxy for the diagnosis of SIBO. A key limitation of LHBT interpretation is the timing of hydrogen measurement, as under physiological conditions, only minimal hydrogen is detectable in breath until fermentation occurs in the cecum, which harbors a high bacterial load. Studies in healthy individuals demonstrate an oro-cecal transit time typically ranging between 72 and 90 minutes ( 11 – 13 ). Accordingly, the North American Consensus guidelines recommend a diagnostic cut-off time of 90 minutes for LHBT interpretation ( 8 ), whereas European guidelines propose shorter cut-off times, in some cases as early as 40 minutes, to reduce false-positive results related to rapid colonic transit, albeit at the expense of sensitivity ( 9 ). With respect to diagnostic hydrogen thresholds, several cut-off levels have been proposed for SIBO diagnosis ( 8 , 9 ). A rise, equal to or greater than (≥) 20 ppm in breath hydrogen, has been adopted in expert consensus recommendations as a standardized criterion, largely to favor the specificity of the test. However, comparative studies demonstrate only modest concordance between breath testing and small bowel aspirate culture ( 14 ), underscoring the absence of a robustly validated hydrogen cut-off. The present study was therefore conducted to optimize diagnostic hydrogen cut-off values for SIBO in patients with irritable bowel syndrome (IBS). Using an optimized transit time framework, breath hydrogen levels were compared between healthy controls and patients with IBS, which were further stratified across different subgroups of IBS. MATERIALS AND METHODS Ethical considerations The need for consent to participate was deemed unnecessary by the Institutional Review Board (IRB) according to national regulations for anonymized data. The study was conducted in accordance with the principles of the Declaration of Helsinki. The study was approved by the Uppsala Institutional Review Board (2022-04646-01); all patients' identities anonymized. Lactulose hydrogen breath test A total of 503 eligible subjects underwent a LHBT. Eligibility required absence of lactase or sucrase deficiency, celiac disease, bile acid malabsorption, inflammatory bowel disease (including ulcerative colitis, Crohn’s disease, collagenous or lymphocytic colitis), gastrointestinal malignancy, or clinical signs of maldigestion. Forty-one individuals were identified as hydrogen non-producers (0 ppm hydrogen in breath) and excluded from further analysis. The remaining 462 subjects were classified according to the Rome III criteria into 92 healthy controls (44 men, 48 women, 19–81 years of age), and 370 patients diagnosed with IBS (156 men, 214 women, 19–77 years of age; 166 diarrhea-dominant (IBS-D), 135 mixed type (IBS-M) and 69 constipation-dominant (IBS-C) ( 15 ). The LHBT was carried out using breath sampling equipment with an electrochemical hydrogen-sensitive cell (GMI Medical Ltd, Renfrew, UK) with a resolution of 1 ppm, accuracy ± 2 ppm, and linear range 2-150 ppm. After an overnight fast from 8:00 PM, breath sampling was performed the following morning at 8:00–10:00 AM. Two baseline end-expiratory breath samples were collected at -10 and 0 min. Thereafter, 10 g of lactulose solution (670 mg/mL; Laktulos Meda, Stockholm, Sweden) was ingested, and breath samples were collected every 10 minutes over the following 180 minutes. During the breath sampling period, the participants were not allowed to exercise, drink, eat, or smoke, as interference may cause falsely high hydrogen levels. Drug treatment with antibiotics, dopamine receptor blockers or opioid receptor agonists, proton pump inhibitors, and laxatives was discontinued at least 28 days before the LHBT was carried out. The breath hydrogen concentration of each subject was plotted as the hydrogen concentration (ppm) against time (min) over the assessment period and measured against baseline. Peak hydrogen values were used to calculate diagnostic accuracy ( 16 ). In a subset of 109 IBS patients, data on antibiotic administration and re-testing after 14 days of treatment were obtained. Statistics Values are presented as mean ± 95% confidence interval within parentheses or mean ± SE as appropriate. Differences between the study groups were calculated using Welch’s t-test and one-way ANOVA, with the healthy control group as the comparator. Validation of the oro-cecal time, as well as peak hydrogen level as a diagnostic cut-off, has previously been verified ( 16 ). Receiver operating characteristics (ROC) were calculated to set the cut-off points and accuracy of the LHBT including sensitivity and specificity. Statistical overlap between the different study groups was calculated by linear-scale kernel density estimates employing the Kolmogorov-Smirnov test. RESULTS After challenge with lactulose, the healthy control group had a mean oro-cecal transit time (OCTT) of 97 (92–102) minutes until the 20 ppm hydrogen level in breath occurred. OCTT of the whole IBS group was 92 (88–96) minutes (ns). The lower limit of the 95% confidence interval of the LHBT transit time in healthy controls showed transit times of 0–80 minutes as evaluable boundaries for the assessment of hydrogen production in the small intestine (cf.16). The LHBT showed expected hydrogen values from 1 ppm to 124 ppm in the whole study group within the 80-minute assessment time frame corresponding to the small bowel (Fig. 1 ). Apparent differences between the IBS subgroups were found by applying the ≥20-ppm hydrogen level and 80-minute readout time as diagnostic cut-offs. IBS-D with high hydrogen levels was clearly separated from controls (p < 0.0001), whereas IBS-M and IBS-C were not (Fig. 2 ). The accuracy of LHBT for the entire IBS group versus controls was evaluated using the 60- and 80-minute OCTT readouts and the ≥20 ppm cut-off. Results showed a better diagnostic accuracy of the 80-minute readout with a sensitivity of 38% at 80 minutes compared with 26% at 60 minutes; both with specificity 77%. The diagnostic performance of the LHBT was further evaluated for the different IBS subgroups IBS-D, IBS-M and IBS-C, employing the 80-minute readout time and ≥ 20 ppm cut-off level. The diagnostic accuracy and odds ratio for IBS-D were superior to those of IBS-M and IBS-C. Additional diagnostic features, such as sensitivity and specificity, as well as positive and negative predictive values, were also better for IBS-D than for IBS-M and IBS-C (Tables 1 a and 1 b). Table 1 a. Diagnostic performance of the lactulose hydrogen breath test over 60 and 80 minutes with a hydrogen cut-off ≥ 20 ppm in patients with irritable bowel syndrome (IBS; n = 370) versus healthy controls (Controls; n = 92). Comparison (time-matched) Sensitivity (%) Specificity (%) Odds Ratio (95% CI) 60 min: All IBS vs Controls 27 77 1.24 (0.72–2.12) 80 min: All IBS vs Controls 38 77 2.03 (1.20–3.46) CI, confidence interval Table 1 b. Diagnostic performance of the lactulose hydrogen breath test over 80 minutes with a hydrogen cut-off ≥ 20 ppm for different IBS subgroups. Healthy controls (n = 92) as reference. IBS subgroup Sensitivity (%) Specificity (%) PPV (%) NPV (%) Accuracy (%) Odds Ratio (95% CI) IBS-D (n = 166) 61 77 83 52 67 5.25 (2.95–9.36) IBS-M (n = 135) 23 77 60 41 45 1.01 (0.54–1.89) IBS-C (n = 69) 10 77 25 53 48 0.38 (0.15–0.96) IBS, irritable bowel syndrome; IBS-D, diarrhea-dominated IBS; IBS-M, mixed IBS; IBS-C, constipation-dominated IBS. Specificity identical across analyses due to the fixed control false-positive rate. CI, confidence interval. Small intestinal bacterial overgrowth in different patient groups The mean peak breath hydrogen level was 10 ( 9 – 12 ) ppm in healthy controls using the 80 minute readout interval. In the whole IBS group, the breath hydrogen level was 20 ( 18 – 23 ) ppm (p < 0.0001 vs. controls). The mean peak values of the different subgroups were as follows: IBS-D 30 ( 26 – 33 ) ppm (p < 0.0001), IBS-C 10 ( 7 – 13 ) ppm (ns) and IBS-M 15 ( 12 – 18 ) ppm (ns), all versus control. Using linear-scale kernel density estimates, the hydrogen overlap between healthy controls and IBS-D was 46%, whereas the overlap with IBS-M was 71% and IBS-C was 82% (Fig. 3 ), reflecting a marked shift of peak hydrogen values towards higher values in IBS-D. Hence, high breath hydrogen was predominantly associated with IBS-D as compared with IBS-M and IBS-C. Among 139 patients classified with high breath hydrogen ≥ 20 ppm, 102 (73%) were recovered in the IBS-D subgroup, while 31 (22%) were found in the IBS-M subgroup and 6 (4%) in the IBS-C subgroup, indicating a strong concordance between high hydrogen production and IBS-D. The breath hydrogen results across all diagnostic subgroups showed that IBS-D retained substantial bacterial hydrogen production compared with IBS-M and IBS-C, (Fig. 4 ). Response to antibiotics As an ad hoc observation, a subset of 109 patients was given antibiotics and re-tested after 14 days of treatment. In the high hydrogen group 31 out of 39 showed a significant reduction of their breath hydrogen levels (p < 0.01). Abdominal symptoms improved in 22. Among 70 patients with low breath hydrogen, none showed any clear change of their breath hydrogen levels, whereas few had mitigated symptoms. DISCUSSION The hydrogen breath test is an accepted non-invasive clinical method to diagnose SIBO because only the microbiota, but not mammalian cells, can produce hydrogen ( 19 ). We found that among patients with IBS, primarily patients with IBS-D are capable of producing high breath hydrogen during the passage of lactulose through the small bowel. For the IBS-M and IBS-C, correspondingly fewer people produce high amounts of hydrogen. This speaks in favour of SIBO as a possible diarreogenic component in IBS-D. The North American consensus for breath testing recommends ≥20 ppm hydrogen level and 90-minute readout time for diagnosis ( 8 ), while the European guidelines do not specify the diagnostic readout time and hydrogen breath levels required for diagnosis ( 9 ). Based on our previous study ( 16 ), we chose a ≥20 ppm increase of hydrogen concentration from baseline within 80 minutes for diagnosis. In this way, we could minimize the risk of over-diagnosing SIBO merely because of rapid transit. Across investigations employing the LHBT, the IBS-D subtype consistently exhibits the highest prevalence of hydrogen-positive SIBO in line with our results ( 17 , 18 ). A study by Rana and Malik ( 20 ) showed that IBS-D patients were predominantly hydrogen-positive, compared with those with IBS-C, while IBS-M showed intermediate results. Later systematic reviews confirmed this tendency, indicating that hydrogen-dominant SIBO occurs preferentially in the diarrhea-predominant IBS phenotype ( 21 ). Although the LHBT may produce false positive results in individuals with rapid oro-cecal transit, this methodological concern does not fully account for the robust hydrogen responses typically observed in IBS-D. Collectively, evidence supports the view that accelerated intestinal transit and small bowel bacterial overgrowth may coexist in a subset of IBS-D patients, suggesting that hydrogen-dominant SIBO represents a key pathophysiological characteristic of diarrhea-predominant IBS ( 21 ). Calculations of the diagnostic accuracy showed that the sensitivity and specificity was optimal using the ≥20-ppm cut-off, with a limited risk of over-diagnosing SIBO. Hence, this cut-off level was used for further diagnostics, in line with the American consensus ( 8 ). Applying a 60-minute cut-off level, the calculated odds ratio was close to unity, indicating limited discriminatory value at this early time point under conditions of a high false positive rate in controls. In contrast, the 80-minute odds ratio was approximately two-fold, supporting a statistically meaningful association between a positive breath hydrogen test and the IBS status at this time point. Our findings reinforce the fact that hydrogen elevations observed at 80 minutes provide greater diagnostic relevance than those obtained at 60 minutes. Employing the 80-minute readout time frame and ≥20 ppm as the cut-off for a proper diagnosis of SIBO, we found that 37% of patients clinically diagnosed with IBS were found to have SIBO. This upholds earlier findings of SIBO in the presence of IBS, in the range of 30–85% of patients with IBS symptoms ( 20 , 22 – 25 ). However, in our hands the number of patients diagnosed with IBS-D represented 73% of the IBS with high hydrogen. This finding suggests a pathophysiological importance of SIBO in IBS-D-like symptoms commensurate with our present findings. However, because SIBO is a complex condition that commonly includes not only symptoms from the gastrointestinal tract, but also malnutrition, neuropathy, muscular atrophy and cachexia, a personalized view on the treatment is mandatory ( 26 , 27 ). Strengths and weaknesses Data were randomly extracted from LHBT records performed for clinical suspicion of SIBO and are therefore considered representative of real-world clinical practice. Symptom reporting may nonetheless be affected by recall bias, despite efforts to clarify uncertain clinical information. Healthy volunteers were included as a comparator to provide normative reference data. Although age may confound SIBO prevalence, this limitation has been well described in both pathophysiological and methodological studies ( 28 ). Lactulose was used as a biomarker in this study because it remains unchanged throughout the small intestine, thereby enhancing the sensitivity of detection for bacterial overgrowth in both the proximal and distal regions of the gut. However, a rapid transit time could be misdiagnosed as SIBO if it reaches the colon sooner than the 80-minute cut-off time. Thus, our finings support a cut-off time of 80 minutes to reduce false positives. In line with this, the European guidelines recommend a standard cut-off timing of 60 minutes to avoid false positives ( 9 ), however, at the cost of false negatives. Elevated breath hydrogen is a marker of intestinal carbohydrate fermentation, which has been associated with diarrhea and accelerated gut transit ( 29 , 30 ). Experimental data suggest that hydrogen itself can modulate motility, particularly in the proximal colon where fermentation and hydrogen production predominates ( 31 ). Clinically, symptom improvement after rifaximin in non-constipated IBS and breath test positive patients occurs even when breath hydrogen does not fully normalize, underscoring that hydrogen is not a single causative factor, but an imperfect marker of fermentation-driven mechanisms ( 32 , 33 ). In conclusion, LHBT is capable of diagnosing SIBO-positive IBS, provided a validated readout time frame and a verified peak hydrogen cut-off level are applied. It is suggested that IBS patients can be subdivided into those who are low or high in breath hydrogen, where high breath hydrogen commonly reflects SIBO manifesting as chronic diarrhea. Declarations Author Contribution Original idea and design of the study by AD and PMH, performance of the study AD, PG, and HJ, calculations and first draft of the manuscript AD under review of PG, HJ, and PMH. Writing of the manuscript by AD and PMH. Acknowledgement Funded by the Region Uppsala, Konung Gustav V och Drottning Viktorias Stiftelse, and Uppsala University. Per M. Hellström was the guarantor of this article. Data available upon request from the guarantor. The late Lars Blomqvist, MD, PhD, is acknowledged for initiating the breath test and quality assessment. Data Availability The data underlying this presentation is available as pseudonymized human data through the guarantor of the article Prof Per M. Hellström, Department of Medical Sciences, Uppsala University, Uppsala, Sweden. References Pimentel M, Lembo A. Microbiome and its role in irritable bowel syndrome. Dig Dis Sci. 2020;65:829–39. 10.1007/s10620-020-06140-5 . Takakura W, Pimentel M. Small intestinal bacterial overgrowth and irritable bowel syndrome—an update. Front Psychiatry. 2020;11:664. 10.3389/fpsyt.2020.00664 . Benno P, Dahlgren AL, Befrits R, Norin E, Hellström PM, Midtvedt T. From IBS to DBS: the dysbiotic bowel syndrome. 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Cite Share Download PDF Status: Published Journal Publication published 06 Apr, 2026 Read the published version in BMC Gastroenterology → Version 1 posted Editorial decision: Revision requested 13 Mar, 2026 Reviews received at journal 11 Mar, 2026 Reviews received at journal 08 Mar, 2026 Reviewers agreed at journal 11 Feb, 2026 Reviewers agreed at journal 10 Feb, 2026 Reviewers agreed at journal 09 Feb, 2026 Reviewers invited by journal 09 Feb, 2026 Editor invited by journal 09 Feb, 2026 Editor assigned by journal 09 Feb, 2026 Submission checks completed at journal 09 Feb, 2026 First submitted to journal 05 Feb, 2026 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. 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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-8800553\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":588831212,\"identity\":\"d1a8f909-001c-4213-b920-270fb44ce93c\",\"order_by\":0,\"name\":\"Atti-La Dahlgren\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Uppsala University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Atti-La\",\"middleName\":\"\",\"lastName\":\"Dahlgren\",\"suffix\":\"\"},{\"id\":588831213,\"identity\":\"e521b13c-395f-492c-9a95-876b67a0a191\",\"order_by\":1,\"name\":\"Per Grybäck\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Karolinska University Hospital\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Per\",\"middleName\":\"\",\"lastName\":\"Grybäck\",\"suffix\":\"\"},{\"id\":588831214,\"identity\":\"8767c0b3-ce62-47aa-87eb-eb85edb562d7\",\"order_by\":2,\"name\":\"Hans Jacobsson\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Karolinska University Hospital\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Hans\",\"middleName\":\"\",\"lastName\":\"Jacobsson\",\"suffix\":\"\"},{\"id\":588831215,\"identity\":\"c8852368-3277-40c7-9d25-6a912e63f1f2\",\"order_by\":3,\"name\":\"Per M Hellström\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCElEQVRIie2QMUsDMRTH3xFIl6dzRLl8hcgtgoJf5VzO5VylQ8GDwnWxH0AQ+xU6dT44SJdg15MsrQXnfgARX+7WhOLmkB8JJOT98vIPQCTyD7mtABjC1cWwHdNs+hFGNb0iELjbmj8rSQ1H6p2ynm8ZjgXKxXz3+fG2Sk837a5J6hbkrPJneV4r9m0EKj3KsoeVzc66QvWKMv5+ShTATmpSOOfnpNwtO4RBEblfkV+k/NDDaqe82qflxgyKXGwDXTgpFcXXTqlsrppyUKALxMcCWtQuS8GyUtvLF5clf79HZQIPG+lkj5ObVE5pUU6spB/bHw6P16mc+eM7PCd0PwbrI5FIJHKUXyT/Wpe6+9sdAAAAAElFTkSuQmCC\",\"orcid\":\"\",\"institution\":\"Uppsala University\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"Per\",\"middleName\":\"M\",\"lastName\":\"Hellström\",\"suffix\":\"\"}],\"badges\":[],\"createdAt\":\"2026-02-05 20:08:16\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-8800553/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-8800553/v1\",\"draftVersion\":[],\"editorialEvents\":[{\"content\":\"https://doi.org/10.1186/s12876-026-04782-w\",\"type\":\"published\",\"date\":\"2026-04-06T15:57:32+00:00\"}],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":102442105,\"identity\":\"07e72f47-82a9-46b4-bfda-48d2222b8d34\",\"added_by\":\"auto\",\"created_at\":\"2026-02-11 17:03:02\",\"extension\":\"png\",\"order_by\":1,\"title\":\"Figure 1\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":17814,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cem\\u003eBreath hydrogen lineup of all subjects included in the study (n=462). Red dashed line indicates 20 ppm cut-off for breath hydrogen. Insert shows detail of the indent in the curve at the diagnostic level 20 ppm.\\u003c/em\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Onlinefloatimage1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-8800553/v1/8076af4f074d387ddc851122.png\"},{\"id\":102442096,\"identity\":\"7262dd75-71f1-4d66-ae22-7d4053e5a194\",\"added_by\":\"auto\",\"created_at\":\"2026-02-11 17:03:01\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":28258,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cem\\u003eBreath hydrogen levels in healthy controls (n = 92) compared with IBS-D (n = 166), IBS-M (n = 135), and IBS-C (n = 69). ns, non-significant.\\u003c/em\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Onlinefloatimage21.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-8800553/v1/ef3574d15e8d93f447ddf838.png\"},{\"id\":102442104,\"identity\":\"93dc031c-eedd-4e4b-926c-6bfb9e83fcb2\",\"added_by\":\"auto\",\"created_at\":\"2026-02-11 17:03:02\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":62588,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eLinear-scale kernel density estimates of peak breath hydrogen concentrations in healthy controls and the IBS subtypes. Distributions are normalized to the percentage of subjects per group. The abscissa shows 0 to 124 ppm with 20-ppm intervals. The ordinata is scaled in 3% increments of the tested population.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-8800553/v1/8922605b2fd48cd425f0f02d.png\"},{\"id\":102745976,\"identity\":\"9355666d-aabd-43bd-8929-4264662c09bb\",\"added_by\":\"auto\",\"created_at\":\"2026-02-16 08:55:03\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":40531,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eDistribution of peak breath hydrogen concentrations by 20-ppm intervals, expressed as percentage of subjects per IBS subgroup. Percentages derived from the area under linear-scale kernel density estimates.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage4.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-8800553/v1/2fe83abdeb986388158a28d3.png\"},{\"id\":106808800,\"identity\":\"048a5fcc-f171-4d48-beba-4c244d0113f4\",\"added_by\":\"auto\",\"created_at\":\"2026-04-13 16:01:42\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":644042,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-8800553/v1/63296b62-12ae-49ae-8ccf-93344a294431.pdf\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"Extended hydrogen breath test analysis for optimized diagnosis of SIBO-positive IBS patients\",\"fulltext\":[{\"header\":\"INTRODUCTION\",\"content\":\"\\u003cp\\u003eAccumulating evidence suggests a potential role for dysbiosis in irritable bowel syndrome (IBS) (\\u003cspan additionalcitationids=\\\"CR2\\\" citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e). Small intestinal bacterial overgrowth (SIBO) is detected in up to 78% of IBS cases (\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e). This sizable prevalence may be attributed to differences in ethnicity, microbiology, and various diagnostic criteria employed. Non-invasive breath tests have gained interest due to the ease and timeliness with which an SIBO diagnosis can be made. Still, bacterial cultures of aspirate from the proximal jejunum are described as the gold standard for diagnosing SIBO (\\u003cspan citationid=\\\"CR5\\\" class=\\\"CitationRef\\\"\\u003e5\\u003c/span\\u003e). However, this has been challenged because it carries a risk of sampling error if not multiple regions of the small bowel are sampled, and the cut-off level for SIBO has been discussed (\\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e). In addition, there is a major contamination risk at sampling, and commonly the sampled bacteria are not culturable; therefore, this diagnostic method is suboptimal (\\u003cspan citationid=\\\"CR5\\\" class=\\\"CitationRef\\\"\\u003e5\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eDifferent types of breath tests have been employed but are hampered by the lack of a true standard for the performance and interpretation of data. Depending on the chosen fermentable bacterial substrate and the timing of readouts and diagnostic hydrogen cut-off levels, various studies arrive at different recommendations for diagnosing SIBO. This has led to interactive working groups advocating essential rules for employing hydrogen breath tests for diagnostic purposes (\\u003cspan additionalcitationids=\\\"CR9\\\" citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eThe lactulose hydrogen breath test (LHBT) is clinically used as a non-invasive proxy for the diagnosis of SIBO. A key limitation of LHBT interpretation is the timing of hydrogen measurement, as under physiological conditions, only minimal hydrogen is detectable in breath until fermentation occurs in the cecum, which harbors a high bacterial load. Studies in healthy individuals demonstrate an oro-cecal transit time typically ranging between 72 and 90 minutes (\\u003cspan additionalcitationids=\\\"CR12\\\" citationid=\\\"CR11\\\" class=\\\"CitationRef\\\"\\u003e11\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eAccordingly, the North American Consensus guidelines recommend a diagnostic cut-off time of 90 minutes for LHBT interpretation (\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e), whereas European guidelines propose shorter cut-off times, in some cases as early as 40 minutes, to reduce false-positive results related to rapid colonic transit, albeit at the expense of sensitivity (\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eWith respect to diagnostic hydrogen thresholds, several cut-off levels have been proposed for SIBO diagnosis (\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e). A rise, equal to or greater than (\\u0026ge;) 20 ppm in breath hydrogen, has been adopted in expert consensus recommendations as a standardized criterion, largely to favor the specificity of the test. However, comparative studies demonstrate only modest concordance between breath testing and small bowel aspirate culture (\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e), underscoring the absence of a robustly validated hydrogen cut-off.\\u003c/p\\u003e \\u003cp\\u003eThe present study was therefore conducted to optimize diagnostic hydrogen cut-off values for SIBO in patients with irritable bowel syndrome (IBS). Using an optimized transit time framework, breath hydrogen levels were compared between healthy controls and patients with IBS, which were further stratified across different subgroups of IBS.\\u003c/p\\u003e\"},{\"header\":\"MATERIALS AND METHODS\",\"content\":\"\\u003cdiv id=\\\"Sec3\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eEthical considerations\\u003c/h2\\u003e \\u003cp\\u003e The need for consent to participate was deemed unnecessary by the Institutional Review Board (IRB) according to national regulations for anonymized data. The study was conducted in accordance with the principles of the Declaration of Helsinki. The study was approved by the Uppsala Institutional Review Board (2022-04646-01); all patients' identities anonymized.\\u003c/p\\u003e \\u003c/div\\u003e\\n\\u003ch3\\u003eLactulose hydrogen breath test\\u003c/h3\\u003e\\n\\u003cp\\u003eA total of 503 eligible subjects underwent a LHBT. Eligibility required absence of lactase or sucrase deficiency, celiac disease, bile acid malabsorption, inflammatory bowel disease (including ulcerative colitis, Crohn\\u0026rsquo;s disease, collagenous or lymphocytic colitis), gastrointestinal malignancy, or clinical signs of maldigestion. Forty-one individuals were identified as hydrogen non-producers (0 ppm hydrogen in breath) and excluded from further analysis. The remaining 462 subjects were classified according to the Rome III criteria into 92 healthy controls (44 men, 48 women, 19\\u0026ndash;81 years of age), and 370 patients diagnosed with IBS (156 men, 214 women, 19\\u0026ndash;77 years of age; 166 diarrhea-dominant (IBS-D), 135 mixed type (IBS-M) and 69 constipation-dominant (IBS-C) (\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eThe LHBT was carried out using breath sampling equipment with an electrochemical hydrogen-sensitive cell (GMI Medical Ltd, Renfrew, UK) with a resolution of 1 ppm, accuracy\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;2 ppm, and linear range 2-150 ppm.\\u003c/p\\u003e \\u003cp\\u003eAfter an overnight fast from 8:00 PM, breath sampling was performed the following morning at 8:00\\u0026ndash;10:00 AM. Two baseline end-expiratory breath samples were collected at -10 and 0 min. Thereafter, 10 g of lactulose solution (670 mg/mL; Laktulos Meda, Stockholm, Sweden) was ingested, and breath samples were collected every 10 minutes over the following 180 minutes. During the breath sampling period, the participants were not allowed to exercise, drink, eat, or smoke, as interference may cause falsely high hydrogen levels. Drug treatment with antibiotics, dopamine receptor blockers or opioid receptor agonists, proton pump inhibitors, and laxatives was discontinued at least 28 days before the LHBT was carried out.\\u003c/p\\u003e \\u003cp\\u003eThe breath hydrogen concentration of each subject was plotted as the hydrogen concentration (ppm) against time (min) over the assessment period and measured against baseline. Peak hydrogen values were used to calculate diagnostic accuracy (\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e). In a subset of 109 IBS patients, data on antibiotic administration and re-testing after 14 days of treatment were obtained.\\u003c/p\\u003e\\n\\u003ch3\\u003eStatistics\\u003c/h3\\u003e\\n\\u003cp\\u003eValues are presented as mean\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;95% confidence interval within parentheses or mean\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;SE as appropriate.\\u003c/p\\u003e \\u003cp\\u003eDifferences between the study groups were calculated using Welch\\u0026rsquo;s t-test and one-way ANOVA, with the healthy control group as the comparator. Validation of the oro-cecal time, as well as peak hydrogen level as a diagnostic cut-off, has previously been verified (\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eReceiver operating characteristics (ROC) were calculated to set the cut-off points and accuracy of the LHBT including sensitivity and specificity.\\u003c/p\\u003e \\u003cp\\u003eStatistical overlap between the different study groups was calculated by linear-scale kernel density estimates employing the Kolmogorov-Smirnov test.\\u003c/p\\u003e\"},{\"header\":\"RESULTS\",\"content\":\"\\u003cp\\u003eAfter challenge with lactulose, the healthy control group had a mean oro-cecal transit time (OCTT) of 97 (92\\u0026ndash;102) minutes until the 20 ppm hydrogen level in breath occurred. OCTT of the whole IBS group was 92 (88\\u0026ndash;96) minutes (ns). The lower limit of the 95% confidence interval of the LHBT transit time in healthy controls showed transit times of 0\\u0026ndash;80 minutes as evaluable boundaries for the assessment of hydrogen production in the small intestine (cf.16).\\u003c/p\\u003e \\u003cp\\u003eThe LHBT showed expected hydrogen values from 1 ppm to 124 ppm in the whole study group within the 80-minute assessment time frame corresponding to the small bowel (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eApparent differences between the IBS subgroups were found by applying the \\u0026ge;20-ppm hydrogen level and 80-minute readout time as diagnostic cut-offs. IBS-D with high hydrogen levels was clearly separated from controls (p\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.0001), whereas IBS-M and IBS-C were not (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe accuracy of LHBT for the entire IBS group versus controls was evaluated using the 60- and 80-minute OCTT readouts and the \\u0026ge;20 ppm cut-off. Results showed a better diagnostic accuracy of the 80-minute readout with a sensitivity of 38% at 80 minutes compared with 26% at 60 minutes; both with specificity 77%.\\u003c/p\\u003e \\u003cp\\u003eThe diagnostic performance of the LHBT was further evaluated for the different IBS subgroups IBS-D, IBS-M and IBS-C, employing the 80-minute readout time and \\u0026ge;\\u0026thinsp;20 ppm cut-off level. The diagnostic accuracy and odds ratio for IBS-D were superior to those of IBS-M and IBS-C. Additional diagnostic features, such as sensitivity and specificity, as well as positive and negative predictive values, were also better for IBS-D than for IBS-M and IBS-C (Tables\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea and \\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb).\\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\\u003ea. Diagnostic performance of the lactulose hydrogen breath test over 60 and 80 minutes with a hydrogen cut-off \\u0026ge;\\u0026thinsp;20 ppm in patients with irritable bowel syndrome (IBS; n\\u0026thinsp;=\\u0026thinsp;370) versus healthy controls (Controls; n\\u0026thinsp;=\\u0026thinsp;92).\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"4\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eComparison (time-matched)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eSensitivity\\u003c/p\\u003e \\u003cp\\u003e(%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eSpecificity\\u003c/p\\u003e \\u003cp\\u003e(%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eOdds Ratio\\u003c/p\\u003e \\u003cp\\u003e(95% CI)\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e60 min: All IBS vs Controls\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e27\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e77\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e1.24 (0.72\\u0026ndash;2.12)\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e80 min: All IBS vs Controls\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e38\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e77\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e2.03 (1.20\\u0026ndash;3.46)\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003ctfoot\\u003e \\u003ctr\\u003e\\u003ctd colspan=\\\"4\\\"\\u003eCI, confidence interval\\u003c/td\\u003e\\u003c/tr\\u003e \\u003c/tfoot\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab2\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 1\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eb. Diagnostic performance of the lactulose hydrogen breath test over 80 minutes with a hydrogen cut-off \\u0026ge;\\u0026thinsp;20 ppm for different IBS subgroups. Healthy controls (n\\u0026thinsp;=\\u0026thinsp;92) as reference.\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"7\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c7\\\" colnum=\\\"7\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eIBS\\u003c/p\\u003e \\u003cp\\u003esubgroup\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eSensitivity (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eSpecificity (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003ePPV (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eNPV (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eAccuracy (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003eOdds Ratio (95% CI)\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eIBS-D (n\\u0026thinsp;=\\u0026thinsp;166)\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e61\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e77\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e83\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e52\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e67\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e5.25\\u003c/p\\u003e \\u003cp\\u003e(2.95\\u0026ndash;9.36)\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eIBS-M (n\\u0026thinsp;=\\u0026thinsp;135)\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e23\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e77\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e60\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e41\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e45\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e1.01\\u003c/p\\u003e \\u003cp\\u003e(0.54\\u0026ndash;1.89)\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eIBS-C\\u003c/p\\u003e \\u003cp\\u003e(n\\u0026thinsp;=\\u0026thinsp;69)\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e10\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e77\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e25\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e53\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e48\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e0.38\\u003c/p\\u003e \\u003cp\\u003e(0.15\\u0026ndash;0.96)\\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\\u003eIBS, irritable bowel syndrome; IBS-D, diarrhea-dominated IBS; IBS-M, mixed IBS; IBS-C, constipation-dominated IBS. Specificity identical across analyses due to the fixed control false-positive rate. CI, confidence interval.\\u003c/p\\u003e\\n\\u003ch3\\u003eSmall intestinal bacterial overgrowth in different patient groups\\u003c/h3\\u003e\\n\\u003cp\\u003eThe mean peak breath hydrogen level was 10 (\\u003cspan additionalcitationids=\\\"CR10 CR11\\\" citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e) ppm in healthy controls using the 80 minute readout interval. In the whole IBS group, the breath hydrogen level was 20 (\\u003cspan additionalcitationids=\\\"CR19 CR20 CR21 CR22\\\" citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e) ppm (p\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.0001 vs. controls). The mean peak values of the different subgroups were as follows: IBS-D 30 (\\u003cspan additionalcitationids=\\\"CR27 CR28 CR29 CR30 CR31 CR32\\\" citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e26\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR33\\\" class=\\\"CitationRef\\\"\\u003e33\\u003c/span\\u003e) ppm (p\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.0001), IBS-C 10 (\\u003cspan additionalcitationids=\\\"CR8 CR9 CR10 CR11 CR12\\\" citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e) ppm (ns) and IBS-M 15 (\\u003cspan additionalcitationids=\\\"CR13 CR14 CR15 CR16 CR17\\\" citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e) ppm (ns), all versus control.\\u003c/p\\u003e \\u003cp\\u003eUsing linear-scale kernel density estimates, the hydrogen overlap between healthy controls and IBS-D was 46%, whereas the overlap with IBS-M was 71% and IBS-C was 82% (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e), reflecting a marked shift of peak hydrogen values towards higher values in IBS-D. Hence, high breath hydrogen was predominantly associated with IBS-D as compared with IBS-M and IBS-C. Among 139 patients classified with high breath hydrogen\\u0026thinsp;\\u0026ge;\\u0026thinsp;20 ppm, 102 (73%) were recovered in the IBS-D subgroup, while 31 (22%) were found in the IBS-M subgroup and 6 (4%) in the IBS-C subgroup, indicating a strong concordance between high hydrogen production and IBS-D.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe breath hydrogen results across all diagnostic subgroups showed that IBS-D retained substantial bacterial hydrogen production compared with IBS-M and IBS-C, (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eResponse to antibiotics\\u003c/p\\u003e \\u003cp\\u003eAs an \\u003cem\\u003ead hoc\\u003c/em\\u003e observation, a subset of 109 patients was given antibiotics and re-tested after 14 days of treatment. In the high hydrogen group 31 out of 39 showed a significant reduction of their breath hydrogen levels (p\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.01). Abdominal symptoms improved in 22. Among 70 patients with low breath hydrogen, none showed any clear change of their breath hydrogen levels, whereas few had mitigated symptoms.\\u003c/p\\u003e\"},{\"header\":\"DISCUSSION\",\"content\":\"\\u003cp\\u003eThe hydrogen breath test is an accepted non-invasive clinical method to diagnose SIBO because only the microbiota, but not mammalian cells, can produce hydrogen (\\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e). We found that among patients with IBS, primarily patients with IBS-D are capable of producing high breath hydrogen during the passage of lactulose through the small bowel. For the IBS-M and IBS-C, correspondingly fewer people produce high amounts of hydrogen. This speaks in favour of SIBO as a possible diarreogenic component in IBS-D.\\u003c/p\\u003e \\u003cp\\u003eThe North American consensus for breath testing recommends \\u0026ge;20 ppm hydrogen level and 90-minute readout time for diagnosis (\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e), while the European guidelines do not specify the diagnostic readout time and hydrogen breath levels required for diagnosis (\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e). Based on our previous study (\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e), we chose a \\u0026ge;20 ppm increase of hydrogen concentration from baseline within 80 minutes for diagnosis. In this way, we could minimize the risk of over-diagnosing SIBO merely because of rapid transit. Across investigations employing the LHBT, the IBS-D subtype consistently exhibits the highest prevalence of hydrogen-positive SIBO in line with our results (\\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e). A study by Rana and Malik (\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e) showed that IBS-D patients were predominantly hydrogen-positive, compared with those with IBS-C, while IBS-M showed intermediate results. Later systematic reviews confirmed this tendency, indicating that hydrogen-dominant SIBO occurs preferentially in the diarrhea-predominant IBS phenotype (\\u003cspan citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e). Although the LHBT may produce false positive results in individuals with rapid oro-cecal transit, this methodological concern does not fully account for the robust hydrogen responses typically observed in IBS-D. Collectively, evidence supports the view that accelerated intestinal transit and small bowel bacterial overgrowth may coexist in a subset of IBS-D patients, suggesting that hydrogen-dominant SIBO represents a key pathophysiological characteristic of diarrhea-predominant IBS (\\u003cspan citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eCalculations of the diagnostic accuracy showed that the sensitivity and specificity was optimal using the \\u0026ge;20-ppm cut-off, with a limited risk of over-diagnosing SIBO. Hence, this cut-off level was used for further diagnostics, in line with the American consensus (\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e). Applying a 60-minute cut-off level, the calculated odds ratio was close to unity, indicating limited discriminatory value at this early time point under conditions of a high false positive rate in controls. In contrast, the 80-minute odds ratio was approximately two-fold, supporting a statistically meaningful association between a positive breath hydrogen test and the IBS status at this time point. Our findings reinforce the fact that hydrogen elevations observed at 80 minutes provide greater diagnostic relevance than those obtained at 60 minutes.\\u003c/p\\u003e \\u003cp\\u003eEmploying the 80-minute readout time frame and \\u0026ge;20 ppm as the cut-off for a proper diagnosis of SIBO, we found that 37% of patients clinically diagnosed with IBS were found to have SIBO. This upholds earlier findings of SIBO in the presence of IBS, in the range of 30\\u0026ndash;85% of patients with IBS symptoms (\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e, \\u003cspan additionalcitationids=\\\"CR23 CR24\\\" citationid=\\\"CR22\\\" class=\\\"CitationRef\\\"\\u003e22\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e). However, in our hands the number of patients diagnosed with IBS-D represented 73% of the IBS with high hydrogen. This finding suggests a pathophysiological importance of SIBO in IBS-D-like symptoms commensurate with our present findings. However, because SIBO is a complex condition that commonly includes not only symptoms from the gastrointestinal tract, but also malnutrition, neuropathy, muscular atrophy and cachexia, a personalized view on the treatment is mandatory (\\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e26\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR27\\\" class=\\\"CitationRef\\\"\\u003e27\\u003c/span\\u003e).\\u003c/p\\u003e\\n\\u003ch3\\u003eStrengths and weaknesses\\u003c/h3\\u003e\\n\\u003cp\\u003eData were randomly extracted from LHBT records performed for clinical suspicion of SIBO and are therefore considered representative of real-world clinical practice. Symptom reporting may nonetheless be affected by recall bias, despite efforts to clarify uncertain clinical information.\\u003c/p\\u003e \\u003cp\\u003eHealthy volunteers were included as a comparator to provide normative reference data. Although age may confound SIBO prevalence, this limitation has been well described in both pathophysiological and methodological studies (\\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e28\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eLactulose was used as a biomarker in this study because it remains unchanged throughout the small intestine, thereby enhancing the sensitivity of detection for bacterial overgrowth in both the proximal and distal regions of the gut. However, a rapid transit time could be misdiagnosed as SIBO if it reaches the colon sooner than the 80-minute cut-off time. Thus, our finings support a cut-off time of 80 minutes to reduce false positives. In line with this, the European guidelines recommend a standard cut-off timing of 60 minutes to avoid false positives (\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e), however, at the cost of false negatives.\\u003c/p\\u003e \\u003cp\\u003eElevated breath hydrogen is a marker of intestinal carbohydrate fermentation, which has been associated with diarrhea and accelerated gut transit (\\u003cspan citationid=\\\"CR29\\\" class=\\\"CitationRef\\\"\\u003e29\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR30\\\" class=\\\"CitationRef\\\"\\u003e30\\u003c/span\\u003e). Experimental data suggest that hydrogen itself can modulate motility, particularly in the proximal colon where fermentation and hydrogen production predominates (\\u003cspan citationid=\\\"CR31\\\" class=\\\"CitationRef\\\"\\u003e31\\u003c/span\\u003e). Clinically, symptom improvement after rifaximin in non-constipated IBS and breath test positive patients occurs even when breath hydrogen does not fully normalize, underscoring that hydrogen is not a single causative factor, but an imperfect marker of fermentation-driven mechanisms (\\u003cspan citationid=\\\"CR32\\\" class=\\\"CitationRef\\\"\\u003e32\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR33\\\" class=\\\"CitationRef\\\"\\u003e33\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eIn conclusion, LHBT is capable of diagnosing SIBO-positive IBS, provided a validated readout time frame and a verified peak hydrogen cut-off level are applied. It is suggested that IBS patients can be subdivided into those who are low or high in breath hydrogen, where high breath hydrogen commonly reflects SIBO manifesting as chronic diarrhea.\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003ch2\\u003eAuthor Contribution\\u003c/h2\\u003e\\u003cp\\u003e Original idea and design of the study by AD and PMH, performance of the study AD, PG, and HJ, calculations and first draft of the manuscript AD under review of PG, HJ, and PMH. Writing of the manuscript by AD and PMH.\\u003c/p\\u003e\\u003ch2\\u003eAcknowledgement\\u003c/h2\\u003e\\u003cp\\u003eFunded by the Region Uppsala, Konung Gustav V och Drottning Viktorias Stiftelse, and Uppsala University. Per M. Hellstr\\u0026ouml;m was the guarantor of this article. Data available upon request from the guarantor. The late Lars Blomqvist, MD, PhD, is acknowledged for initiating the breath test and quality assessment.\\u003c/p\\u003e\\u003ch2\\u003eData Availability\\u003c/h2\\u003e\\u003cp\\u003eThe data underlying this presentation is available as pseudonymized human data through the guarantor of the article Prof Per M. Hellstr\\u0026ouml;m, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\u003cli\\u003e\\u003cspan\\u003ePimentel M, Lembo A. Microbiome and its role in irritable bowel syndrome. Dig Dis Sci. 2020;65:829\\u0026ndash;39. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003e10.1007/s10620-020-06140-5\\u003c/span\\u003e\\u003cspan address=\\\"10.1007/s10620-020-06140-5\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eTakakura W, Pimentel M. Small intestinal bacterial overgrowth and irritable bowel syndrome\\u0026mdash;an update. Front Psychiatry. 2020;11:664. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003e10.3389/fpsyt.2020.00664\\u003c/span\\u003e\\u003cspan address=\\\"10.3389/fpsyt.2020.00664\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eBenno P, Dahlgren AL, Befrits R, Norin E, Hellstr\\u0026ouml;m PM, Midtvedt T. 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N Engl J Med. 2011;364:22\\u0026ndash;32. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003e10.1056/NEJMoa1004409\\u003c/span\\u003e\\u003cspan address=\\\"10.1056/NEJMoa1004409\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003ePimentel M, Park S, Mirocha J, Kane SV, Kong Y. Effect of a nonabsorbed oral antibiotic on IBS symptoms. Ann Intern Med. 2006;145:557\\u0026ndash;63. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003e10.7326/0003-4819-145-8-200610170-00004\\u003c/span\\u003e\\u003cspan address=\\\"10.7326/0003-4819-145-8-200610170-00004\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\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\":\"info@researchsquare.com\",\"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\":\"Hydrogen, IBS, Lactulose, Microbiota, Small intestinal bacterial overgrowth, SIBO\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-8800553/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-8800553/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eBackground: Small intestinal bacterial overgrowth (SIBO) is suggested in irritable bowel syndrome (IBS). Optimal hydrogen levels and time frame for diagnosing SIBO are still under discussion. Our primary aim was to consolidate a discriminating threshold for a positive lactulose hydrogen breath test (LHBT) in IBS. As a secondary aim, we optimized the diagnostic time frame for the small bowel.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003eMethods: LHBT was performed on 503 subjects who met the inclusion criteria. After excluding non-hydrogen producers, the remaining 462 subjects were 92 healthy individuals and 370 IBS patients. Peak hydrogen levels were compared as mean values with 95% confidence intervals.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003eResults: At the 80-min orocecal cutoff , healthy subjects showed a peak hydrogen of 10(9–12) ppm compared with 20(18–23) ppm in the overall IBS group (p \\u0026lt;0.0001). Using ≥20 ppm cutoff , sensitivity was 38% and specificity 77%. Peak hydrogen was highest in IBS-D (30(26-33) ppm; p \\u0026lt;0.0001), intermediate in IBS-M (14(11-17) ppm), and lowest in IBS-C (10(7-13) ppm), showing sensitivities of 61%, 23%, and 10%, respectively, with specificity 77%. After antibiotics, IBS patients with low hydrogen were unchanged, whereas most with high hydrogen reduced their hydrogen levels (p \\u0026lt;0.01).\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003eConclusion: Using a cutoff level of 20 ppm during the first 80 minutes, LHBT can diagnose SIBO in people with IBS showing high breath hydrogen, as compared with those having low breath hydrogen. Hence, SIBO-positive patients can be separated from SIBO-negative IBS patients. To this end, a majority of SIBO-positive subjects respond to antibiotic treatment.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Extended hydrogen breath test analysis for optimized diagnosis of SIBO-positive IBS patients\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2026-02-11 17:02:51\",\"doi\":\"10.21203/rs.3.rs-8800553/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0},{\"type\":\"decision\",\"content\":\"Revision requested\",\"date\":\"2026-03-13T18:46:07+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2026-03-11T17:40:14+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2026-03-08T15:41:00+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"137359696038959071619356573322270661862\",\"date\":\"2026-02-11T15:20:44+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"317802364938895087774014773990509445153\",\"date\":\"2026-02-10T09:06:46+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"229178345855821697888777164912889044440\",\"date\":\"2026-02-09T18:29:45+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewersInvited\",\"content\":\"\",\"date\":\"2026-02-09T13:05:24+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorInvited\",\"content\":\"\",\"date\":\"2026-02-09T12:40:22+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorAssigned\",\"content\":\"\",\"date\":\"2026-02-09T08:49:03+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"checksComplete\",\"content\":\"\",\"date\":\"2026-02-09T08:41:33+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"submitted\",\"content\":\"BMC Gastroenterology\",\"date\":\"2026-02-05T19:55:42+00:00\",\"index\":\"\",\"fulltext\":\"\"}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"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\":\"2a725907-82f9-4a5a-94f6-3f74933bb240\",\"owner\":[],\"postedDate\":\"February 11th, 2026\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"published-in-journal\",\"subjectAreas\":[],\"tags\":[],\"updatedAt\":\"2026-04-13T16:00:16+00:00\",\"versionOfRecord\":{\"articleIdentity\":\"rs-8800553\",\"link\":\"https://doi.org/10.1186/s12876-026-04782-w\",\"journal\":{\"identity\":\"bmc-gastroenterology\",\"isVorOnly\":false,\"title\":\"BMC Gastroenterology\"},\"publishedOn\":\"2026-04-06 15:57:32\",\"publishedOnDateReadable\":\"April 6th, 2026\"},\"versionCreatedAt\":\"2026-02-11 17:02:51\",\"video\":\"\",\"vorDoi\":\"10.1186/s12876-026-04782-w\",\"vorDoiUrl\":\"https://doi.org/10.1186/s12876-026-04782-w\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-8800553\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-8800553\",\"identity\":\"rs-8800553\",\"version\":[\"v1\"]},\"buildId\":\"XKTyCvWXoU3ODBz1xrDgd\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}