AIM:To evaluate the reproducibility of a modified ~(13)Cbreath test-based measurement of solid phase gastricemptying(GE)within the frames of a simple-repeatedmeasure study protocol.METHODS:Twelve healthy subjects(6 females and6 males,mean age 24.9±0.7 years)were recruited toundergo three identical GE examinations.In six subjectsthe first two examinations were performed 2 d apart,and the third session was carried out at a medianinterval of 19.5 d(range 18-20d)from the second one.In another six subjects the first two measurements weretaken 20 d apart(median,range:17-23 d),whereasthe third session took place 2 d after the second one.Probes of expiratory air collected before and during sixhours after intake of a solid meal(378 kcal)labelledwith 75 μL(68 mg)~(13)C-octanoic acid,were measuredfor ~(13)CO_2 enrichment with the nondispersive isotope-selective infrared spectrometry NDIRS apparatus.RESULTS:Taking coefficients of variation for pairedexaminations into account,the short-term reproducibilityof the GE measurement was slightly but not significantlybetter than the medium-term one:7.7% and 11.2% forthe lag phase(T-Lag),7.3% and 10.9% for the gastrichalf emptying time(T 1/2).The least differences in GEparameters detectable at P=0.05 level in the 12 pairedexaminations were 9.6 and 15.6 min for T-Lag,11.6 and19.7 min for T 1/2 by a two-day or two to three-week time gap,respectively.CONCLUSION:The low-cost modification of thebreath test involving a lower dose of ~(13)C-octanoic acidand NDIRS,renders good short-and medium-termreproducibility,as well as sensitivity of the measurementof gastric emptying of solids. AIM: To evaluate the reproducibility of a modified Cbreath test-based measurement of solid phase gas modulation (GE) within the frames of a simple-repeated measurement study protocol. METHODS: Twelve healthy subjects (6 females and 6 males, mean age 24.9 ± 0.7 years) were recruited toundergo three identical GE examinations.In six subjectsthe first two examinations were performed 2 d apart, and the third session was carried out at a median interval of 19.5 d (range 18-20d) from the second one. Another six subjects the first two measurements weretaken 20 d apart (median, range: 17-23 d), where last 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) labeled with 75 μL (68 mg) ~ (13) C-octanoic acid, were measured for CO 2 enrichment with the nondispersive isotope-selective infrared spectrometry NDIRS apparatus .RESULTS: Taking coefficients of variation for pairedexaminations into account, the short -term repro ducibilityof the GE measurement was slightly but not significantlybetter than the medium-termone: 7.7% and 11.2% forthe lag phase (T-Lag), 7.3% and 10.9% for the gastrichalf emptying time in GEparameters detectable at P = 0.05 level in the 12 pairedexaminations were 9.6 and 15.6 min for T-Lag, 11.6 and 19.7 min for T 1/2 by a two-day or two to three-week time gap, respectively. CONCLUSION: The low-cost modification of the breth test involving a lower dose of ~ (13) C-octanoic acid and NDIRS, renders good short-and medium-term reproducibility, as well as sensitivity of the measurement of gastric emptying of solids.