Background: 13C-octanoic acid breath test (13C-OABT) is a simple, safe and non-invasive technique for measuring gastric emptying. However, the method has not been standardized yet. Aim of the study was to work up, introduce and evaluate our own method of the 13C-OABT for adults.
Methods and results: Ten healthy volunteers entered the study (5 men, 5 women, mean age 32 years, 50 % Helicobacter pylori positive). Standard test meals (with 100 mg 13C-sodium octanoate) were used three times within 3 weeks. The same solid meal (1,178 kJ) for Tests 1 and 2 contained scrambled egg (+ 3 g oil), white bread (40 g), butter (10 g) and distilled water (200 ml). Semi-solid meal (1,020 kJ) for Test 3 contained milk pudding (200 g) and distilled water (200 ml). Duplicate breath samples were obtained before and every 15 minutes after eating the test meal during 255 minutes. Altogether 1,080 breath samples were analysed twice (isotope ratio mass spectrometry, AP2003 Analytical Precision, UK). To assess the half-life of elimination (t1/2 E), we modelled the process of elimination with the incomplete gamma-function, which has a convenient form for the empiric plotting of breath test data. Mean t1/2E was 136+/-10 minutes (Test 1), 134+/-14 (Test 2) and 123+/-16 minutes (Test 3). Clinical reproducibility of 13C-OABT in particular persons was 98.2% (18 breath samples series), 90.8 % (15 samples) and 87.1% (9 breath samples series). There was a significant correlation between Test 1 and Test 2 results (r=0.887, p<0.0001). Mean difference of duplicate breath sample analysis was 1.460 % (in 540 pairs), mean baseline one-day analysis difference was 0.0982 (99.9274% accuracy). In healthy volunteers, normal range of t1/2E is 110-160 minutes for solids and 91-155 minutes for semisolid test meal. Using our own computed mean time of intermediate metabolism of 13C-octanoic acid (76.5+/-7.5 minutes), gastric emptying half-time is 33.5-83.5 minutes for solids and 14.5-78.5 minutes for semisolid test meal in healthy volunteers.
Conclusions: The 13C-OABT is accurate non-invasive method for gastric emptying measurement.