Gastric Alimetry® Test Interpretation in Gastroduodenal Disorders: Review and Recommendations

Abstract

Chronic gastroduodenal symptoms are prevalent worldwide, and there is a need for new diagnostic and treatment approaches. Several overlapping processes may contribute to these symptoms, including gastric dysmotility, hypersensitivity, gut–brain axis disorders, gastric outflow resistance, and duodenal inflammation. Gastric Alimetry® (Alimetry, New Zealand) is a non-invasive test for evaluating gastric function that combines body surface gastric mapping (high-resolution electrophysiology) with validated symptom profiling. Together, these complementary data streams enable important new clinical insights into gastric disorders and their symptom correlations, with emerging therapeutic implications. A comprehensive database has been established, currently comprising > 2000 Gastric Alimetry tests, including both controls and patients with various gastroduodenal disorders. From studies employing this database, this paper presents a systematic methodology for Gastric Alimetry test interpretation, together with an extensive supporting literature review. Reporting is grouped into four sections: Test Quality, Spectral Analysis, Symptoms, and Conclusions. This review compiles, assesses, and evaluates each of these aspects of test assessment, with discussion of relevant evidence, example cases, limitations, and areas for future work. The resultant interpretation methodology is recommended for use in clinical practice and research to assist clinicians in their use of Gastric Alimetry as a diagnostic aid and is expected to continue to evolve with further development.

Short‐ and long‐term reproducibility of body surface gastric mapping using the Gastric Alimetry® system

“…Total symptom burden was higher for patients than controls, across the duration of the test. Further details on how to interpret the spectrograms and symptom profiles can be found in Foong et al 37 . and Varghese et al 41…”

“…Standard exclusion criteria for a Gastric Alimetry test were applied (breastfeeding, pregnancy, previous major gastric surgery, adhesive allergies, or damaged epigastric skin) 36 . Additionally, participants were only included if their first test showed good technical quality, as outlined previously (e.g., <50% artifact detected, >50% of the meal consumed) 36,37 . Participants were excluded if they had significant physical or medication changes since their original test (e.g., weight loss/gain of more than 10 kg, change in medications that affect the stomach, or significant medical procedures or surgeries).…”

“…Gastric Alimetry provides a single spectrogram for each test, summated from the top‐ranked channels of the electrode array, which describes the frequency and amplitude content of the recorded signals as a function of time 26 . These spectrograms were used to compute four spectral metrics for analyses, described in detail elsewhere 36,37,39 : BMI‐Adjusted Amplitude (μV): characterizes the strength of the recorded gastric activity as an average of the whole‐test amplitude, adjusted for BMI. Gastric Alimetry Rhythm Index™ (GA‐RI): a measure of the concentration of amplitude in the gastric frequency band over time (between 0 and 1), which characterizes the rhythmic stability of the recorded gastric activity; also adjusted for BMI. Principal Gastric Frequency (cpm): characterizes the frequency associated with stable, persistent gastric activity as defined by GA‐RI. Fed: Fasted Amplitude Ratio (ff‐AR): characterizes the responsiveness to a meal stimulus, which is calculated as a ratio of the maximal 1‐h average postprandial amplitude to the amplitude in the preprandial period. …”

“…The participants were independently categorized into phenotypes for each of the three tests based on the normative intervals of the Gastric Alimetry metrics 36,37 . Gastric dysfunction was categorized as low rhythm stability (GA‐RI <0.25), low amplitude (BMI‐Adjusted Amplitude <22 μV), high amplitude (>70 μV), high frequency (>3.35 cpm), and low frequency (<2.65 cpm) 36 …”

Nausea and Gastric Myoelectrical Activity are Influenced by Hormonal Contraception in Chronic Gastroduodenal Disorders

“…Participants fasted overnight before undergoing non-invasive BSGM using a high-resolution 64-electrode array connected to a wearable reader device (Gastric Alimetry TM , Alimetry, New Zealand) (22). Following a 30-minute fasting recording, participants consumed an energy bar (Clif Bar ™ Nutrition Bar Chocolate Chip; 250 kcal, 5 g fat, 45 g carbohydrate, 10 g protein, 7 g fibre; Clif Bar & Company, Emeryville, CA) and nutrient drink (Ensure ™ , 230 kcal, 230 mL; Abbott Nutrition, Chicago, IL) and continued recording for a further 4 hours postprandially, per a standardized testing methodology (21,27). Continuous symptom monitoring was achieved using a validated symptom logging app, prompting subjects every 15 minutes to rate their nausea, bloating, upper gut pain, heartburn, stomach burn and excessive fullness on 0-10 visual analogue Likert scales (0 indicating no symptoms; 10 indicating the worst imaginable extent of symptoms) (24).…”