Influence of caloric intake on gastric emptying of solids assessed by C-13-octanoic acid breath test

Background: The C-13-octanoic breath test (C-13-OBT), a recently developed technique to evaluate gastric emptying of solids, has been validated in com parison to scintigraphy with low caloric meals (250 kcal). However, there i s consensus that for clinical studies total caloric load should be in exces s of 300 kcal. but studies comparing C-13-OBT results after low and medium caloric meals are lacking. Methods: Ten healthy subjects were given a 250-k cal and a 550-kcal meal in randomized order. Gastric emptying was assessed simultaneously by ultrasonography and C-13-OBT. Breath samples were taken a ccording to both classic (21 samples over 5 h) and simplified (11 samples) schedules. Results: Increasing the meal energy content resulted in signific antly longer half emptying time (T-1/2) estimates by both ultrasonography ( P < 0.01, Wilcoxon test) and C-13-OBT (P < 0.05). T-1/2 estimates by the tw o methods significantly correlated for both the 250 (r(s) = 0.733, P = 0.01 8) and the 550 (r(s) = 0.637, P = 0.035) kcal meal. However, differences be tween T-1/2 estimates by C-13-OBT and ultrasonography were greater after th e 550- than the 250-kcal meal (median 172.5 versus 76.5 min, P < 0.05). Int erindividual variability was also 2-fold greater for indexes estimated by C -13-OBT with the 550-kcal meal compared with the 250-kcal meal. For both me als C-13-OBT yielded similar results with the classic and simplified schedu les. Conclusions: In healthy subjects caloric intake is a major determinant of gastric emptying rate. However, after a medium caloric meal C-13-OBT sh ows some inaccuracy, which raises questions about its routine clinical appl ication. Nevertheless, when using C-13-OBT one must take into account that the simplified schedule is just as effective as the classic one, and is far lower in cost.