Background
Current classification schemes for chronic gastroduodenal symptoms substantially overlap and therefore do not clearly guide patient-specific therapy. Gastric Alimetry is a new test of gastric function encompassing simultaneous spectral (frequency and amplitude) electrophysiology, and time-of-test patient-reported symptom capture. We hypothesised that a mechanism-based approach to gastroduodenal disorder classification may offer a valid and more specific alternative scheme.

Methods
We performed a multicentre, prospective cohort study of patients meeting Rome-IV criteria for functional dyspepsia (FD) and chronic nausea and vomiting syndromes (CNVS). Gastric Alimetry™ (Alimetry, New Zealand) was used for body surface gastric mapping spectral analysis and time-of-test symptom profiling (Figure 1). A standardised digital classification framework separated patients into those with a) abnormal spectral analyses (based on principal gastric frequency, BMI-adjusted amplitude, and Gastric Alimetry Rhythm Index, a measure of the stability of the gastric frequency); normal spectral analyses with b) symptoms related to the gastric amplitude (sensorimotor, post-gastric, and activity-relieved); and c) symptoms un-related to gastric amplitude (continuous, meal-relieved, meal-induced; Figure 1).

Results
210 patients (80% female, median age 37) of whom 169 met criteria for CNVS and 206 met criteria for FD (79% overlapping) were included. Overall, 83% with unexplained gastroduodenal symptoms were phenotyped, with 79/210 (37.6%) classified as having a spectral abnormality on gastric mapping. Of the remaining 131, 37 (17.6%) were classified as ‘continuous pattern’, 28 (13.3%) as ‘meal-induced pattern’, and 15 (7.1%) as ‘sensorimotor pattern’. When spectral analyses were normal, symptom patterns that were independent of gastric amplitude such as continuous, meal-relieved, and meal-induced patterns were more strongly correlated with depression and anxiety (PHQ-2: exp(β) 2.38, p = 0.024), STAI-SF score: exp(β) 1.21, p = 0.021). Phenotypes and their relative prevalence are summarised in Figure 2.

Conclusion
Spectral measures of gastric electrophysiology and standardised time-of-test symptom profiles offer a novel approach to classifying patients based on proposed mechanisms of disease. These groupings correlated with chronic symptoms, quality of life, and psychological factors, demonstrating initial clinical validity.

Emma Uren

Appearances