AIM: To evaluate the reproducibility of a modified 13C breath test-based measurement of solid phase gastric emptying (GE) within the frames of a simple-repeated measure study protocol.METHODS: Twelve healthy subjects (6 females and 6 males, mean age 24.9±0.7 years) were recruited to undergo three identical GE examinations. In six subjects the first two examinations were performed 2 d apart,and the third session was carried out at a median interval of 19.5 d (range 18 - 20 d) from the second one.In another six subjects the first two measurements were taken 20 d apart (median, range: 17-23 d), whereas the third session took place 2 d after the second one.Probes of expiratory air collected before and during six hours after intake of a solid meal (378 kcal) labelled with 75 μL (68 mg) 13C-octanoic acid, were measured for 13CO2 enrichment with the nondispersive isotopeselective infrared spectrometry NDIRS apparatus.RESULTS: Taking coefficients of variation for paired examinations into account, the short-term reproducibility of the GE measurement was slightly but not significantly better than the medium-term one: 7.7% and 11.2% for the lag phase (T-Lag), 7.3% and 10.9% for the gastric half emptying time (T1/2). The least differences in GE parameters detectable at P= 0.05 level in the 12 paired examinations were 9.6 and 15.6 min for T-Lag, 11.6 and 19.7 min for T1/2 by a two-day or two to three-week time gap, respectively.CONCLUSION: The low-cost modification of the breath test involving a lower dose of 13C-octanoic acid and NDIRS, renders good short- and medium-term reproducibility, as well as sensitivity of the measurement of gastric emptying of solids.