Normative values for body surface gastric mapping evaluations of gastric motility using Gastric Alimetry: spectral analysis

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Introduction Body surface gastric mapping (BSGM) is a new non-invasive test of gastric function. BSGM offers several novel and improved biomarkers of gastric function capable of differentiating patients with overlapping symptom-profiles. The aim of this study was to define normative reference intervals for BSGM spectral metrics in a population of healthy controls. Methods BSGM was performed in healthy controls using Gastric Alimetry (Alimetry, New Zealand) comprising a stretchable high-resolution array (8×8 electrodes; 196 cm 2 ), wearable Reader, and validated symptom-logging App. The evaluation encompassed a fasting baseline (30 min), 482 kCal meal, and 4-hr postprandial recording. Normative reference intervals were calculated for BSGM metrics including the Principal Gastric Frequency, Gastric Alimetry Rhythm Index (GA-RI; a measure of the concentration of power in the gastric frequency band over time), BMI-adjusted amplitude (µV), and fed:fasted amplitude ratio (ff-AR). Data are reported as median and reference interval (5 th and/or 95 th percentiles). Results 110 subjects (55% female, median age 32 (IQR 24 – 50), median BMI 23.8 kg/m 2 (IQR 21.4 – 26.9)) were included. The median Principal Gastric Frequency was 3.04 cpm; reference interval: 2.65 – 3.35 cpm. Median GA-RI was 0.50; reference interval: !0.25. Median BMI-adjusted amplitude was 37.6 µV; reference interval: 20-70 µV. The median ff-AR was 1.85; reference interval !1.08. Higher BMI was associated with a shorter meal-response duration (p=0.014). Conclusions This study provides normative reference intervals for BSGM spectral data that will be used in clinical practice to inform diagnostic interpretations of abnormal gastric function.