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

Background: The 13C-octanoic breath test (13C-OBT), a recently developed technique to evaluate gastric emptying of solids, has been validated in comparison to scintigraphy with low caloric meals (250 kcal). However, there is consensus that for clinical studies total caloric load should be in excess of 300 kcal, but studies comparing 13C-OBT results after low and medium caloric meals are lacking.

Methods: Ten healthy subjects were given a 250-kcal and a 550-kcal meal in randomized order. Gastric emptying was assessed simultaneously by ultrasonography and 13C-OBT. Breath samples were taken according to both classic (21 samples over 5 h) and simplified (11 samples) schedules.

Results: Increasing the meal energy content resulted in significantly longer half emptying time (T(1/2)) estimates by both ultrasonography (P < 0.01, Wilcoxon test) and 13C-OBT (P < 0.05). T(1/2) estimates by the two methods significantly correlated for both the 250 (r(s) = 0.733, P = 0.018) and the 550 (r(s) = 0.637, P = 0.035) kcal meal. However, differences between T(1/2) estimates by 13C-OBT and ultrasonography were greater after the 550- than the 250-kcal meal (median 172.5 versus 76.5 min, P < 0.05). Interindividual variability was also 2-fold greater for indexes estimated by 13C-OBT with the 550-kcal meal compared with the 250-kcal meal. For both meals 13C-OBT yielded similar results with the classic and simplified schedules.

Conclusions: In healthy subjects caloric intake is a major determinant of gastric emptying rate. However, after a medium caloric meal 13C-OBT shows some inaccuracy, which raises questions about its routine clinical application. Nevertheless, when using 13C-OBT one must take into account that the simplified schedule is just as effective as the classic one, and is far lower in cost.