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Review
. 2023 Oct 10;12(20):6436.
doi: 10.3390/jcm12206436.

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

Daphne Foong  1 , Stefan Calder  2   3   4 , Chris Varghese  2 , Gabriel Schamberg  3   4 , William Xu  2 , Charlotte Daker  5 , Vincent Ho  1   6 , Christopher N Andrews  7 , Armen A Gharibans  2   3   4 , Greg O'Grady  2   3   4
Affiliations
Review

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

Daphne Foong et al. J Clin Med. .

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.

Keywords: body surface gastric mapping; chronic nausea and vomiting; disorders of gut brain interaction; functional dyspepsia; gastroparesis; motility disorders.

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Conflict of interest statement

G.O. and A.A.G. hold intellectual property and grants in gastric electrophysiology and are Directors of University of Auckland spin-out companies (G.O.: Alimetry, Insides Company; A.A.G.: Alimetry); S.C., G.S., and C.N.A are members of Alimetry. The remaining authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Gastric Alimetry setup. (a) Gastric Alimetry device consisting of a high-resolution electrode array (8 × 8 pregelled Ag/AgCl electrodes), Alimetry Reader and Gastric Alimetry app; (b) Device positioned over the epigastrium; (c) Gastric Alimetry App consisting of symptom logging; (d) Alimetry Cloud where clinicians can access and store Gastric Alimetry patient reports.
Figure 2
Figure 2
Summary of ‘Test Quality’ guidelines. (a) Checking impedance for electrode signal quality is ‘good’ for at least half the electrodes; (b) Checking meal completion is above 50%; (c) Checking proportion of artifacts is less than 50%; (d) Checking app usage was at least every 15 min; (e) Checking raw signal traces for uncertainties in artifacts.
Figure 3
Figure 3
Summary of ‘Spectral Analysis’ guidelines. (a) Normal reference intervals for Gastric Alimetry as generated from a large database of healthy adults from diverse demographics (n = 110). Four statistically independent spectral metrics are defined with reference to the standardized 4.5 h test protocol: Gastric Alimetry Rhythm Index (GA-RI), Principal Gastric Frequency, Fed:Fasted Amplitude Ratio and Average Amplitude [22]. Reprinted with permission from ref. [25]. Copyright 2023, CC BY 4.0 DEED; (b) Assess amplitude curves for meal response: note that the high fasting baseline is a common normal variant; (c) Assess for transient abnormalities that may not have been detected in the overall summary metrics.
Figure 4
Figure 4
Summary of ‘Symptoms’ guidelines. (a) Assess for symptom baseline (red box); (b) Assess whether symptoms are meal-responsive or meal non-responsive (red box); (c) Assess the symptom curve pattern: declining curve, continuous curve or late uptrending curve (red arrows); (d) Assess for correlation between symptom curves and gastric amplitude (red box); (e) Assess the timing, type and number of discrete symptom events.
Figure 5
Figure 5
Emerging methods to objectively correlate gastric symptom profiles with gastric activity. (a) Example of weak correlation between symptoms and gastric amplitude; (b) Example of strong correlation between symptoms and gastric amplitude.
Figure 6
Figure 6
Example of a normal Gastric Alimetry spectral analysis, with a ‘sensorimotor’ phenotype profile.
Figure 7
Figure 7
Example of an abnormal Gastric Alimetry spectral analysis.
Figure 8
Figure 8
Additional considerations for artifacts. (a) Example of an extrinsic movement artifact where they appear as large spikes in amplitude (upper red box) and artifactual signal traces shown in the grey line (bottom red box); (b,c) Example of colonic intrinsic artifacts showing low-frequency spectral scatter occurring with the Principal Gastric Frequency band and minimal movement artifacts (b), and true gastric dysrhythmia showing low-frequency spectral scatter occurring with an absent Principal Gastric Frequency band and minimal movement artifacts (c).
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