Beyond the Snapshot: Overcoming GES Limitations to Characterize Gastric Phenotypes and Therapeutic Responses Using a 6-Day Ambulatory Wearable Monitor.

Background Gastric emptying scintigraphy (GES) is considered the standard for differentiating gastroparesis from functional dyspepsia and other foregut disorders characterized by nausea and vomiting but provides only a brief physiologic snapshot that may not accurately reflect daily function. We utilized a non‐invasive wireless patch system (WPS) to characterize multiday gastric myoelectrical activity, evaluate its relationship with GES, and assess changes following a therapeutic intervention.

Adults referred for GES for symptoms thought to represent gastroparesis were enrolled in a prospective study. Patients wore a WPS for up to 6 days, starting on the day of scintigraphy. Gastric myoelectrical activity was analyzed and categorized into relatively weak, relatively moderate, and relatively strong activity phenotypes. A subset of patients underwent repeat monitoring following individualized therapeutic interventions (e.g., anti‐emetics, proton pump inhibitors, lifestyle changes).

Forty‐eight patients (mean age 44; 79% female) completed the study. GES identified delayed gastric emptying in 18%, rapid in 22%, and normal in 60% of subjects. During the 4‐h concurrent GES window, gastric activity in patients with delayed emptying was lower, but this difference did not reach statistical significance (p = 0.08). When compared to the full multiday recording period, GES results showed no correlation with the myoelectric readings. Significant day‐to‐day variability was observed, both random and systemic. In the latter category, a “Test‐Day” dip was observed with gastric activity lowest on Day 1 (GES test day) and increasing significantly on subsequent days, stabilizing by Day 4 (p < 0.001). Healthy control subjects recorded during normal daily routines showed no such day‐to‐day variation. In the retesting cohort, anti‐emetics produced robust increases in gastric amplitude, whereas PPIs showed minimal impact.

The WPS effectively captures distinct gastric phenotypes and quantifies physiologic responses to therapy in both gastric and intestinal regions, demonstrating its clinical utility as a robust tool for evaluating and managing foregut symptoms in real‐world settings. Importantly, the multiday WPS highlights significant day‐to‐day physiologic variability in gastric activity that extends beyond the single‐day GES ‘snapshot’.

day‐to‐day variability, dyspepsia, gastric motility, gastroparesis, nausea, wearable wireless patch Keypoints Diagnostic Limitation of gastric scintigraphy revealed: Current diagnostic testing for gastroparesis provides only a static snapshot and fails to capture the day‐to‐day variability of gastric function. The “Test Day” Effect: Multiday wireless monitoring revealed that gastric myoelectrical activity is significantly suppressed on the day of scintigraphy compared to subsequent days. Therapeutic Monitoring: Ambulatory monitoring successfully quantified objective physiologic improvements following treatment with anti‐emetics, offering a novel biomarker for treatment response. Plain Language Summary To explore whether a standard 4‐h hospital‐based test provides a complete picture of how a person's stomach functions day‐to‐day, researchers had 48 patients with stomach symptoms wear a continuous, non‐invasive wireless tracking patch for up to 6 days. The study indicated that stomach activity can fluctuate significantly from day to day; for example, activity was generally lowest on the day of the hospital‐based test but appeared to stabilize a few days later. This suggests that a single short test might not always capture the full scope of a patient's condition. The researchers concluded that this multi‐day wireless patch shows promise as a practical tool for monitoring real‐world stomach function, and it could potentially help doctors see how certain treatments, like anti‐nausea medications, are impacting stomach function. Gastric Emptying Scintigraphy (GES) remains widely used to diagnose gastroparesis but provides a 4‐h static snapshot. Multiday gut tracking revealed a “Test‐Day” dip, with gastric activity significantly suppressed on the day of the GES test that later stabilizes. Continuous monitoring may better reflect real‐world gastrointestinal function and better capture therapeutic response. 1. Introduction Upper gastrointestinal (GI) symptoms—including nausea, early satiety, postprandial fullness, bloating, and epigastric discomfort—are exceedingly common [1, 2, 3]. Yet these symptoms are highly nonspecific, arising from a broad spectrum of underlying pathophysiologic processes [4] such as chronic nausea and vomiting syndrome (CNVS), delayed gastric emptying, impaired gastric accommodation [5], visceral hypersensitivity [6], and/or regional dysmotility [7]. Because clinical symptoms alone cannot accurately distinguish these different pathophysiologic processes, objective testing is frequently employed to ensure an accurate diagnosis and guide therapeutic decision‐making [8, 9]. Gastric emptying scintigraphy (GES) remains the most widely used test to differentiate gastroparesis from functional dyspepsia and other foregut disorders characterized by nausea and vomiting, such as CNVS. However, GES provides only a single, brief snapshot of gastric function, capturing neither the day‐to‐day variability nor the complex interplay of gastric and intestinal function that may drive symptoms. Indeed, prior work [10, 11] has shown that the reproducibility of GES is limited, with nearly one‐third of patients receiving a different classification of gastric emptying on repeat testing. Patients with similar symptom profiles may have markedly different underlying physiology profiles that contribute to their day‐to‐day symptoms, and the diagnostic yield of GES alone can be limited. The wireless patch system (WPS) (GutTracker, G‐Tech Medical Inc.) has been shown to be a safe and effective ambulatory test providing up to 6 days of continuous gastric and intestinal myoelectrical recordings. Prior work has demonstrated its value in characterizing physiological patterns in patients with symptoms of functional dyspepsia and in those with delayed gastric emptying [12]. However, changes in gastrointestinal myoelectrical activity following therapeutic interventions have not previously been described. The ability of the WPS to conveniently monitor gastrointestinal physiology over multiple days after treatment offers a unique opportunity to assess dynamic, treatment‐related changes under real‐world conditions. Building on earlier studies, this prospective investigation integrates an expanded cohort of patients, some of whom underwent repeat monitoring after individualized therapeutic interventions. The overall aims of this study were to: (1) characterize day‐to‐day patterns of gastrointestinal myoelectrical activity in patients with symptoms of chronic nausea and vomiting referred for GES; (2) evaluate the relationship between gastric myoelectrical activity and GES outcomes; and (3) evaluate changes in these activity patterns following therapeutic interventions individualized at the discretion of the clinician who ordered the gastric emptying scan. 2. Methods Adult patients (≥ 18 years of age) referred to Mayo Clinic Jacksonville for a 4‐h, solid phase, GES for evaluation of bothersome upper GI symptoms thought to represent foregut dysfunction, including CNVS, gastroparesis, and functional dyspepsia were eligible for study inclusion. IRB approval was obtained. Patients were contacted in advance to determine whether they would be willing to participate in a research study. Consent was obtained remotely prior to the visit or in person on the day of the study. Gastric emptying was performed using a standardized protocol previously described [13]. In brief, the patient ingested an egg white test meal labeled with 99Tc over 15 min. Scintigraphy was performed over 4 h. The percentage of material emptied from the stomach was reported at 1, 2, and 4 h. Gastric emptying scans were characterized as: normal (75% or more emptied at 4 h); delayed ( 65% emptied at 1 h). Demographic information was collected at baseline, including age, gender, race, the predominant symptom leading to gastric scintigraphy being scheduled, other gastrointestinal symptoms, duration of symptoms, prior gastrointestinal surgery, and comorbid conditions such as diabetes. Patients were excluded from the study if: they had undergone prior gastric or esophageal surgery; had surgery to the GI tract within the last 60 days (e.g., appendectomy, cholecystectomy); were on chronic opioids or other medications known to affect gastric emptying (e.g., GLP‐1 agonists, high dose tricyclic agents); were recently hospitalized for complications of diabetes or had a HbA1c > 10; had severe psychological distress preventing study participation; or were unable to read or understand the consent form. Three wireless motility patches (WPS) paired to a smartphone app (Figure 1) were applied to the skin on the day of the GES test; patients were instructed to wear the patches for 6 days. Two were applied above the umbilicus, centered approximately 5 cm from the midline. One was applied and centered approximately 5 cm below the umbilicus. Verification of patch function was confirmed at bedside using the installed patch monitor app (the “app”) on an iPhone. A second test was conducted using the same protocol following individualized therapeutic interventions, including adjustments in medication and/or lifestyle changes on the subset of patients who were retested. Baseline tests were conducted between Aug 2022 and July 2024. Post intervention tests were conducted between September 2024 and November 2024. Patients were asked to consume three meals daily following their normal pattern, and to record the time of meal ingestion (using the iPhone app). Patients were not instructed on specific caloric intake. Patients were allowed to shower but asked not to completely submerge in water, so as not to affect the integrity/function of the patch system, for the duration of the study. The app periodically uploads the encrypted patch data and events to a secure cloud server. Upon completion of the test, the raw data was downloaded from the cloud and analyzed. Historic data recorded with the wireless patches from healthy control subjects acquired during normal daily activities is included. Patch processing has been described in detail before [12, 14, 15, 16]. In brief, processing of the patch data included removal of large amplitude artifacts followed by Fourier transformation to frequency space over selected time subintervals. The resulting spectra were normalized [15] by dividing with a quiet reference region of the frequency spectrum to reduce variability related to patient‐specific factors and recording conditions. Peaks were identified in the 1 to 28 cpm range in each time subinterval and subsequently assigned to gastric (2.4 to 3.8 cpm), intestinal (5 to 12 cpm) and colonic (12 to 28 cpm) ranges. The energy within these peak ranges were summed to calculate gastric, intestinal, and colonic activity. Gastric electrical activity is characterized by a narrow ~3 cpm [17] signal that matches established frequency and peak‐width signatures for the stomach. Established literature using both invasive [18] and surface electrodes [19] defines a descending frequency gradient in the human intestine, 12.5 cpm in the duodenum to 8.6 cpm in the terminal ileum. SmartPill [15, 20] and manometry [21] measurements concordant with the wireless patches confirm that the majority of 8–12 cpm activity originates in the small intestine. Colonic frequencies [22, 23, 24] span three ranges—2–6 cpm, 9–12 cpm, and 12–40 cpm with the 12–28 cpm the most prominent colonic frequency seen in the wireless patches. The activity was calculated in the following categories: the 4‐h period concurrent to the scintigraphy test, every 24‐h period for the daily activity and over the complete multiday test period. Patients were classified into relatively weak ( 25th and 75th percentile) gastric groups based on their time‐averaged full‐test gastric activity. 2.1. Statistical Analysis of Day‐To‐Day Variability in Gastric Activity Gastric myoelectrical activity was calculated over each 24‐h recording period and expressed as the percent change from each subject's individual mean across all recording days, yielding a within‐subject normalized measure. Between‐day comparisons within each cohort (Mayo patients and healthy controls) were performed using the two‐sided Mann–Whitney U test, a non‐parametric rank‐based test for non‐normally distributed data and unequal group sizes. Day 1 was compared independently against each of Days 2 through 5. To control for the inflation of Type I error arising from multiple pairwise comparisons, raw p‐values were adjusted using the Benjamini‐Hochberg false discovery rate. Statistical significance was set at a corrected p‐value threshold of 0.05. All analyses were performed in Python using the SciPy. Stats and stats models libraries. 2.2. Intervention Patient records were reviewed to determine the type of intervention employed after the results of the GES were transmitted to the ordering provider. Standardized treatment regimens were not employed; treatments were individualized at the discretion of the ordering provider. 2.3. Responder Analysis To robustly distinguish true treatment effects from natural physiological fluctuations, treatment response was evaluated using a within‐subject repeated measures design in which each patient served as their own control, providing inherent protection against inter‐subject variability. Meaningful treatment response was operationalized using a Reliable Change Index (RCI), which quantifies whether the change in post‐treatment mean activity is statistically significant relative to each patient's own baseline variability. Because baseline recording length varied across subjects, the significance threshold was computed individually for each patient using their own baseline standard deviation and number of available recording days, rather than applying a single population‐level cutoff. This ensures that subjects with shorter baselines—and therefore greater uncertainty in their mean estimate—are held to an appropriately more conservative threshold. For each patient, the standard deviation (sᵢ) of daily activity was calculated across their individual baseline period of nᵢ days, and the subject‐specific significance threshold was defined as: where 1.96 corresponds to the 95% confidence level. A subject was classified as a responder if the difference between their post‐treatment and baseline means exceeded their individually derived threshold. 3. Results 3.1. Demographics Fifty‐one subjects referred for symptoms thought to represent gastroparesis were enrolled across the two studies (mean age 44 years; mean BMI 27 kg/m2; 79% female). 3.2. Gastric Scintigraphy All patients completed the 4‐hour scintigraphic scan without incident. Subject demographics, test results, and interventions are shown in Table 1. Nine subjects (18%; eight female) demonstrated delayed gastric emptying; eleven subjects (21%; eight female) demonstrated rapid emptying at the 2‐hour point; and thirty‐one subjects (60%; 24 female) demonstrated normal emptying. TABLE 1. | No | Subject | Sex | 4 h% | GES result | Final diagnosis | Treatment | |---|---|---|---|---|---|---| | 1 | MCJA121 | f | 36 | Delayed emptying | Gastroparesis | Prokinetic | | 2 | MCJA011 | f | 48 | Delayed emptying | Gastroparesis | Anti‐emetic | | 3 | MCJA016 | f | 55 | Delayed emptying | Gastroparesis | Anti‐emetic, Prokinetic | | 4 | MCJA102 | f | 55 | Delayed emptying | Gastroparesis | Anti‐emetic, Prokinetic | | 5 | MCJA125 | m | 67 | Delayed emptying | Reflux and nausea | Anti‐emetic, PPI | | 6 | MCJA019 | f | 70 | Delayed emptying | Achalasia | Diet change only | | 7 | MCJA013 | f | 71 | Delayed emptying | Gastroparesis | Prokinetic | | 8 | MCJA101 | f | 72 | Delayed emptying | Gastroparesis | Diet change only | | 9 | MCJA127 | f | 72 | Delayed emptying | Functional dyspepsia | Neuromodulator | | 10 | MCJA004 | f | 79 | Normal emptying | Functional dyspepsia | Neuromodulator | | 11 | MCJA017 | f | 81 | Normal emptying | Functional dyspepsia | Neuromodulator | | 12 | MCJA009 | f | 82 | Normal emptying | Functional dyspepsia | Neuromodulator | | 13 | MCJA105 | f | 83 | Normal emptying | Chronic nausea | Anti‐emetic | | 14 | MCJA015 | f | 83 | Normal emptying | Functional dyspepsia | Diet change only | | 15 | MCJA023 | f | 86 | Normal emptying | Functional dyspepsia | Neuromodulator | | 16 | MCJA012 | f | 86 | Normal emptying | Symptomatic gallstones | No change | | 17 | MCJA104 | m | 87 | Normal emptying | Functional dyspepsia | Diet change only | | 18 | MCJA110 | f | 87 | Normal emptying | Functional dyspepsia | Neuromodulator | | 19 | MCJA021 | f | 87 | Normal emptying | Functional dyspepsia | PPI | | 20 | MCJA005 | f | 88 | Normal emptying | Functional dyspepsia, reflux | PPI | | 21 | MCJA020 | f | 89 | Normal emptying | Chronic nausea | Anti‐emetic | | 22 | MCJA006 | f | 89 | Normal emptying | Functional dyspepsia | FDGard | | 23 | MCJA122 | f | 90 | Normal emptying | Endometriosis | No change | | 24 | MCJA118 | f | 91 | Normal emptying | Functional dyspepsia | Anti‐emetic, Diet change | | 25 | MCJA002 | m | 91 | Normal emptying | Gastritis | Cleared for lung transplant | | 26 | MCJA124 | f | 92 | Normal emptying | Reflux | PPI | | 27 | MCJA107 | f | 93 | Normal emptying | Chronic constipation and nausea | PPI | | 28 | MCJA010 | m | 93 | Normal emptying | Reflux | PPI | | 29 | MCJA003 | f | 94 | Normal emptying | Chronic nausea | Anti‐emetic | | 30 | MCJA109 | f | 94 | Normal emptying | Chronic nausea | Anti‐emetic | | 31 | MCJA113 | f | 95 | Normal emptying | Chronic nausea | Anti‐emetic | | 32 | MCJA111 | f | 95 | Normal emptying | Functional dyspepsia | Anti‐emetic | | 33 | MCJA128 | f | 97 | Normal emptying | Functional dyspepsia, reflux | No change | | 34 | MCJA108 | m | 97 | Normal emptying | Functional dyspepsia | PPI | | 35 | MCJA106 | m | 97 | Normal emptying | Type II diabetes | Metformin dosage increased | | 36 | MCJA112 | f | 99 | Normal emptying | Chronic nausea | Anti‐emetic | | 37 | MCJA123 | f | 99 | Normal emptying | Constipation | Prokinetic | | 38 | MCJA126 | m | 99 | Normal emptying | Functional dyspepsia | Neuromodulator | | 39 | MCJA117 | f | 99 | Normal emptying | Pelvic floor dysfunction | Miralax | | 40 | MCJA022 | m | 100 | Normal emptying | Functional dyspepsia | Neuromodulator | | 41 | MCJA103 | f | 96 | Rapid, normal emptying | Functional dyspepsia | Diet change only | | 42 | MCJA014 | f | 97 | Rapid, normal emptying | Functional dyspepsia, reflux | PPI | | 43 | MCJA120 | f | 98 | Rapid, normal emptying | Functional dyspepsia | PPI | | 44 | MCJA119 | m | 98 | Rapid, normal emptying | Functional dyspepsia | PPI | | 45 | MCJA007 | f | 98 | Rapid, normal emptying | Reflux | PPI | | 46 | MCJA115 | m | 98 | Rapid, normal emptying | Reflux | Fundoplication | | 47 | MCJA001 | f | 98 | Rapid, normal emptying | Chronic nausea | Neuromodulator | | 48 | MCJA116 | m | 99 | Rapid, normal emptying | Chronic nausea | Anti‐emetic | | 49 | MCJA114 | f | 99 | Rapid, normal emptying | Constipation | Miralax | | 50 | MCJA008 | f | 99 | Rapid, normal emptying | Functional dyspepsia | Neuromodulator | | 51 | MCJA018 | f | 99 | Rapid, normal emptying | Rumination syndrome | Diet change only | Note: Rapid emptying classification based on 2 h emptying percentages > 65%. Bold: Subjects 106, 107, 108, 109, 113, 114, 116, 117, 123, 124, 125 were re‐tested. 66% (six out of nine) of the patients with delayed emptying were diagnosed with gastroparesis; the other three had a mild delay (67%, 70%, and 72%) in gastric emptying and, based on symptoms and other clinically indicated tests, were classified as having FD, achalasia, and gastroesophageal reflux disease with nausea, respectively. In patients with normal or rapid emptying, FD represented the largest group, followed by chronic nausea and gastroesophageal reflux disease, with other diagnoses such as constipation, pelvic floor dysfunction, and diabetes‐related symptoms occurring less frequently (see Table 1). 3.3. Therapeutic Interventions Individuals with delayed emptying were predominantly prescribed anti‐emetics and prokinetics, followed by PPIs and a small particle size diet. Individuals with rapid gastric emptying and normal emptying were treated with a wide range of interventions; neuromodulators and PPIs were the dominant therapeutic choices. 3.4. GutTracker Test Forty‐eight (94%) patients successfully completed the GutTracker tests with an average test length of 4.5 days. iOS App and patch issues resulted in loss of data from three patients which was not included in the analysis. Figure 2 shows the frequency dot plot of the detected peaks for an individual subject for the full 6‐day test and for the first day which included the GES test period. 3.5. Gastric Activity From GutTracker Test vs. GES Results Figure 3 shows the gastric activity distribution from the GutTracker test grouped by gastric emptying classification from GES—rapid, normal and delayed emptying for the 4‐h concurrent period and from the full test. During the 4‐h concurrent period, the delayed emptying group demonstrated lower activity compared to the normal emptying group, although the difference did not reach statistical significance (p = 0.08). When analyzed across the full multiday recording period, the GES results showed no correlation with the myoelectric readings. 3.6. Distribution of Gastric Activity From the Full Test A histogram in Figure 4A shows total gastric myoelectrical activity summed over the multiday test. Vertical dashed lines mark the 25th and 75th percentiles of the distribution, used to stratify subjects into “relatively weak”, “relatively moderate,” and “relatively strong” gastric activity groups. Subjects with delayed gastric emptying on scintigraphy are highlighted in red and were distributed across the three groups. Figure 4B presents the corresponding average gastric GutPrints for each activity group. The relatively weak‐activity group (< 25th percentile, 2.2E+05) exhibited low, broadly distributed power with minimal spectral peaks, the relatively moderate group (25th–75th percentile) showed a weakly defined peak near 3 cpm, and the relatively strong‐activity group (> 75th percentile, 4.3E+05) demonstrated a pronounced and narrow peak in the gastric range. The 25th and 75th percentile values for the gastric myoelectrical activity summed over the multiday test for the historic healthy control group were at 2.8E+05 and 4.8E+05, respectively. 3.7. Daily Variations in Gastric Activity Across the Normal Emptying and Delayed Emptying Groups The box and scatter plot in Figure 5A depicts the daily percent change in gastric activity relative to each subject's mean value across the recording period. Each point represents an individual subject on a given day, with color denoting gastric emptying category (gray = normal emptying, pink = delayed emptying). Median values (black horizontal bars) are shown for each day, and pairwise significance between days is indicated by brackets. A progressive and statistically significant increase in gastric activity was observed after day 1, which was the day of the GES test, with activity rising steadily and then stabilizing through Day 4 (p < 0.001). Six of the 43 subjects were classified as having delayed gastric emptying based on their GES results. In this subgroup, the day‐to‐day pattern paralleled that of the overall cohort, with gastric activity on days 4 and 5 higher than on day 1 though not statistically significant (p = 0.076). The box and scatter plot in Figure 5B shows the daily percentage change in gastric activity for a historic healthy control cohort group. The healthy control subjects did not demonstrate significant day‐to‐day variation. The panel on the right illustrates the mean ± IQR of the gastric GutPrint for each day for the respective cohorts. To further characterize the magnitude of the Day 1 effect at the individual subject level for the Mayo cohort, Figure 6 presents the distribution of within‐subject percent differences between Day 1 activity and the average of Days 4 and 5. While the median difference was approximately 32%, indicating that gastric activity on Day 1 was on average 32% lower than during the stabilized later recording days, the distribution reveals substantial heterogeneity across subjects. Most participants had Day 1 gastric activity suppressed by 25% to 75%, but one subject showed nearly 100% suppression compared to later days. 3.8. Re‐Testing Data Eleven subjects agreed to a retest with the GutTracker following a therapeutic intervention (see Table 1). The intervention and the repeat GutPrint data are described below. 3.9. The Effects of Anti‐Emetics and PPI Therapy on Gastric Activity Figure 7 shows the baseline and post‐intervention GutPrints for the intervention groups. The three subjects prescribed anti‐emetics (leftmost column) showed post‐intervention increases in gastric activity, with two subjects (109 and 116) exceeding the individual RCI significance thresholds, with post‐intervention ratios of 5.4× and 3.6× relative to baseline (Table 2), respectively. The third anti‐emetic subject (113) showed a more modest, non‐significant ratio of 1.5×. In contrast, the three subjects prescribed a PPI (second column) exhibited minimal or no changes that exceeded RCI significance thresholds in gastric activity. Another subject (MCJA125) that was prescribed both an anti‐emetic and PPI showed a significant decrease in both gastric and intestinal activity. TABLE 2. | Subject/treatment | Baseline Days | Post Days | Gastric 2.4–4 cpm | Intestinal 5.0–12 cpm | Colon 12.0–28 cpm | |---|---|---|---|---|---| | Anti‐emetics (n = 3) | ||||| | 109 Phenergan | 4 | 2 | 5.4× * (+441%, thr: 32%) | 1.8× (+79%, thr: 88%) | 1.6× (+56%, thr: 140%) | | 113 Zofran | 7 | 3 | 1.5× (+51%, thr: 65%) | 0.6× (−35%, thr: 113%) | 1.2× (+25%, thr: 67%) | | 116 Zofran | 5 | 3 | 3.6× * (+265%, thr: 53%) | 1.1× (+13%, thr: 112%) | 0.4× * (−59%, thr: 57%) | | PPIs (n = 3) | ||||| | 107 Omeprazole | 5 | 6 | 1.0× (−3%, thr: 91%) | 1.2× (+16%, thr: 78%) | 0.6× (−39%, thr: 48%) | | 108 Protonix | 5 | 6 | 1.1× (+8%, thr: 103%) | 1.1× (+13%, thr: 126%) | 0.3× * (−68%, thr: 52%) | | 124 Nexium 20 mg | 8 | 6 | 0.5× (−45%, thr: 60%) | 0.8× (−18%, thr: 56%) | 0.6× (−39%, thr: 50%) | | Anti‐emetic + PPI (n = 1) | ||||| | 125 Zofran + Nexium 40 mg | 2 | 4 | 0.1× * (−95%, thr: 56%) | 0.4× * (−59%, thr: 54%) | 0.4× (−64%, thr: 241%) | | Metformin (n = 1) | ||||| | 106 Metformin 500 mg BID | 5 | 5 | 2.2× * (+121%, thr: 66%) | 1.9× * (+89%, thr: 70%) | 1.0× (−4%, thr: 50%) | | Miralax/PT/Linaclotide (n = 3) | ||||| | 114 Miralax | 5 | 1 | 1.5× (+48%, thr: 63%) | 1.0× (−2%, thr: 47%) | 0.9× (−9%, thr: 96%) | | 117 Miralax + PT | 3 | 4 | 0.6× (−43%, thr: 76%) | 0.4× (−62%, thr: 103%) | 0.2× (−77%, thr: 118%) | | 123 Linaclotide 290 mcg | 5 | 4 | 1.0× (+4%, thr: 50%) | 1.3× * (+28%, thr: 25%) | 0.6× (−39%, thr: 69%) | Change exceeds individual RCI significance threshold (thr). Ratio = post‐intervention ÷ baseline mean amplitude. Spectral amplitude ratios (post‐intervention ÷ baseline mean amplitude) are shown for 11 subjects grouped by treatment. Ratios greater than 1.0 indicate an increase in band activity following intervention; ratios less than 1.0 indicate a decrease. Values in parentheses show the absolute percentage change and the individual significance threshold, derived from each subjects own baseline variability using the Reliable Change Index (RCI; threshold = 1.96 × SEM × √2). Bold and an asterisk (*) denote a significant response (p < 0.05), defined as an absolute change exceeding the individual RCI threshold. Baseline Days and Post Days reflect the number of recording days contributing to the respective mean amplitude estimates. Frequency bands correspond to dominant electrical signatures of gastric (2.4–3.8 cpm), small intestinal (5.0–12 cpm), and colonic (12.0–28 cpm) myoelectrical activity. 3.10. Understanding Day‐To‐Day Gastric Activity Pre‐ and Post‐Intervention in a Patient With Type II Diabetes Figures 7 (fourth column) and 8 illustrate the gastric peak activity for an individual with Type II diabetes treated with an increased dosage of metformin for the full test and on a day‐by‐day basis. The individual additionally reduced alcohol consumption and lost several pounds. Gastric activity increased significantly with a post‐intervention ratio of 2.2× (Table 2) relative to baseline, exceeding the individual RCI significance threshold. Notably, intestinal activity also increased significantly with a ratio of 1.9×, likewise surpassing the significance threshold, suggesting a broader improvement in upper and mid‐gastrointestinal motility beyond the gastric compartment alone. 3.11. Understanding the Effect of Medical Interventions Focused on Treating Constipation MiraLAX: Two subjects with normal gastric emptying (per scintigraphy) were treated with polyethylene glycol 3350. One subject was diagnosed with chronic constipation, and another subject was diagnosed with pelvic floor dysfunction. Neither subject showed an increase in intestinal and colonic activity post‐intervention, with the subject with pelvic floor dysfunction showing overall lower activity. Linaclotide: The subject's GES test was normal, and management was focused on constipation using daily linaclotide (290 mcg daily). Post‐intervention testing revealed a significant increase in intestinal activity with a ratio of 1.3× (Table 2) that was greater than the RCI threshold. Colonic signals demonstrated a decrease at the 13 cpm peak with a concurrent broadening and enhancement of activity across 13–20 cpm, along with the emergence of additional frequency components. 3.12. Adverse Events One subject reported local irritation and redness at one of the patch sites that resolved with the use of an over‐the‐counter steroidal cream. 4. Discussion In this prospective study of adults referred for evaluation of suspected gastroparesis, we demonstrate that a 6‐day ambulatory wireless patch system provides meaningful physiological information that extends beyond the diagnostic capability of a single GES, with the added advantage of enabling easy, repeatable retesting to evaluate treatment response and/or evolving symptoms. While GES remains the gold standard for diagnosing gastroparesis, it represents a single physiologic snapshot. In our study, during the 4‐h concurrent GES window, gastric activity in patients with delayed emptying was indeed lower, although this difference did not reach statistical significance. However, when compared to the full multiday recording period, the 4‐h GES results unsurprisingly lost any correlation with the myoelectrical readings. The full‐test distribution of gastric activity revealed a broad range of gastric activity—each with distinct spectral patterns. Despite the modest sample size, the distinct separation in the distribution between the relatively weak, moderate, and strong groups suggests underlying physiological groupings within this population. Subjects with delayed emptying were distributed across the weak, moderate, and strong activity groups defined by their multiday WPS results, suggesting that gastric motor physiology fluctuates substantially from day to day. This is important from a clinical standpoint, as it offers a potential explanation for why patients with similar symptoms do not uniformly respond to a single class of medication, and why the severity of symptoms does not always correlate with the degree of gastric emptying delay identified on GES. Daily analysis demonstrated sizeable fluctuations in gastric activity within individuals. Activity was lowest on the day of the gastric emptying study and increased significantly on subsequent days, stabilizing around day 4. These findings have two important implications. First, gastric activity measured during a standardized test day after an overnight fast may not represent typical physiologic function. Conditions inherent to the test—such as fasting, disruptions to usual routines, and test‐related stress—may transiently suppress gastric myoelectrical activity. Indeed, a representative subject with delayed emptying exhibited a 50‐percentage‐point swing between daily amplitudes. Second, the observed trajectory of recovery and stabilization over several days suggests that gastric myoelectrical activity is dynamic and context‐dependent, and that meaningful physiologic patterns may only emerge outside the constraints of a single test day. This day‐to‐day variability highlights the value of longer ambulatory physiologic monitoring to accurately characterize gastric function and identify patient‐specific patterns that would otherwise be missed by conventional snapshot testing. Third, the gastric scintigraphy test meal is both low‐fat and low volume, which may not reflect a typical meal with subsequent gastric and intestinal myoelectric changes. This study provides the first multiday physiologic characterization of response to common therapeutic interventions in patients undergoing evaluation for suspected gastroparesis. Among the three subjects treated with anti‐emetics, two demonstrated post‐intervention increases in gastric myoelectrical activity that exceeded their individually derived RCI significance thresholds, with ratios of 5.4× and 3.6× relative to baseline. The third subject showed a more modest, non‐significant change of 1.5×. In contrast, the three subjects prescribed a PPI exhibited minimal changes that did not exceed their individual RCI thresholds, consistent with prior findings [25, 26, 27]. These findings suggest that improvement in gastric myoelectrical activity may serve as a physiologic biomarker of treatment response for neuromodulator or prokinetic therapy. The individual with type II diabetes similarly demonstrated more than a two‐fold increase in gastric activity following intensification of metformin therapy and lifestyle changes, with improvements evident across most days of the retest. This observation is consistent with prior ultrasonographic studies showing that restoration of glycemic control can enhance gastric motor function in diabetic patients with gastroparesis [28]. This case highlights the ability of multiday monitoring to capture meaningful physiologic changes even when a patient remains within the same activity phenotype. Such individualized physiologic profiling may be particularly useful in patients with complex metabolic or neurogenic motility disorders. Interventions targeting the intestine and colon showed heterogeneous responses. Subjects treated with polyethylene glycol for constipation or pelvic floor dysfunction did not demonstrate increases in intestinal or colonic activity, aligning with the drug's osmotic—not motor‐stimulating—mechanism. In contrast, linaclotide produced marked increases in intestinal peak activity with redistribution of colonic frequency components, consistent with known effects on secretion, fluid movement, and intestinal motility. These findings reinforce that different pharmacologic classes influence gastrointestinal motor physiology in distinct and measurable ways, and multiday myoelectrical monitoring may help clarify these effects in real‐world settings. This work demonstrates that ambulatory gastric myoelectrical monitoring provides clinically relevant information beyond gastric emptying. The ability to: (1) capture physiologic variability over multiple days; (2) classify patients into graded gastric activity phenotypes; and (3) quantify individualized physiological responses to treatment in real‐world conditions could materially improve how foregut disorders are evaluated and managed. For providers, identifying whether symptoms arise in the context of weak vs. strong gastric activity may guide selection of prokinetics, neuromodulators, or behavioral interventions. For patients, the system offers a noninvasive way to objectively assess response to therapy without repeated visits for invasive diagnostic testing, which are associated with some risks. Like all research studies, this study has several limitations. One, the sample size of subjects undergoing retesting was modest. Two, therapeutic interventions were individualized rather than standardized, limiting the ability to draw causal conclusions. In the ideal world, larger groups of patients in each category would be treated with one specific therapy. This highlights the need for a future, larger, randomized controlled trial to confirm these findings. Three, these studies involved patients referred for gastric scintigraphy, and the results may not apply to those with symptoms not thought to represent a predominant foregut disorder such as delayed gastric emptying. Four, most patients were female, although no significant differences were identified between genders. Five, only two patients with concomitant constipation symptoms were treated for those symptoms (PEG and linaclotide). The responses were quite different, which is intriguing, although no firm claims regarding mechanisms and therapeutic implications can be made based on this limited sample size. In summary, a multiday wearable patch system provides novel information into gastric, intestinal, and colonic myoelectrical function that cannot be captured by a single GES. Gastric activity demonstrates substantial day‐to‐day variability and captures physiologic responses to interventions that can be quantified objectively in real‐world settings. These data support the use of noninvasive, prolonged ambulatory monitoring as a complementary tool for evaluating foregut symptoms, phenotyping patients, and assessing therapeutic response. Author Contributions B.E.L. and D.J.C. were responsible for study design, study performance, and data collection. All authors were involved in data analysis and drafting and editing this manuscript. Conflicts of Interest Lindsay Axelrod, Steve Axelrod and Anand Navalgund are employees of G‐Tech Medical. Data Availability Statement The data that support the findings of this study are available from the corresponding author upon reasonable request.

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