Adolescent Normative Intervals for Body Surface Gastric Mapping: Spectral Analysis

Abstract Objective Body surface gastric mapping (BSGM) non-invasively assesses gastric myoelectrical activity along with real-time symptom reporting. In adults, the development of normative intervals has underpinned new explanatory phenotypes, aiding clinical decision-making. This study established normative reference intervals for adolescent BSGM metrics. Study Design Healthy adolescents aged 12-17 years with a BMI <35 kg/m 2 were recruited from New Zealand, Australia and the United States. BSGM using Gastric Alimetry (Alimetry, New Zealand) involved a 30-minute fast, followed by a 480-kcal meal, and a 4-hour postprandial recording. Reference intervals were calculated for four validated metrics: Principal Gastric Frequency (PGF), body mass index (BMI)-adjusted amplitude, Gastric Alimetry Rhythm Index (GA-RI, indicating rhythm stability), and the fed-to-fasted amplitude ratio (ff-AR). Results were reported at the median and 5th and/or 95th percentiles as appropriate. Results A total of 107 participants (52.8% female, median age 14 [IQR 13-16], median BMI 20.1 [IQR 18.75-22.40]) with mixed ethnicities were included. No substantive correlations were observed between BSGM metrics and demographics or anthropometric data. Therefore, a single set of normative reference intervals was established. Median PGF was 3.06 cycles per minute; reference interval 2.72-3.37. Median BMI-adjusted amplitude was 37.80 µV; reference interval 20.0-72.0. Median GA-RI was 0.51; reference interval ≥0.22. Median ff-AR was 2.12; reference interval ≥1.0. Conclusion This study presents normative reference intervals for BSGM spectral metrics in adolescent populations, informing the interpretation of tests in research and clinical practice.