The C-13-mixed triglyceride breath test in healthy adults

Defects in lipolysis due to pancreatic insufficiency can be diagnosed by the mixed triglyceride (MTG) (CO2)-C-13 breath test. However, the effects of various test conditions on the (CO2)-C-13 response have only been partially elucidated. In healthy adults, we performed the (CO2)-C-13 mixed triglyceride breath test and we compared (a) the inter- and intra-individual variation in the (CO2)-C-13 response; (b) the effect of two different test meals; (c) the effect of an additional meal during the test; and (d) the effect of physical exercise during the test. Upon repeating the test in the same individual (test meal cream), repeatability coefficients were large, with respect to either time to maximum C-13 excretion rate (3.8 h), maximum C-13 excretion rate (4.9% C-13 dose h(-1)) or cumulative recovery of C-13 over the 9-h study period (22.7% C-13 dose). The cumulative C-13 expiration over 9 h obtained with the test meal composed of cream was quantitatively similar to that obtained with bread and butter: 42.2 +/- 8.4% and 47.7 +/- 6.3% respectively. Fasting for 9 h during the test resulted in similar C-13 expiration rates and cumulative C-13 expiration (43.4% +/- 7.2%) when compared with consumption of an additional meal 3 h after the start of the test (38.3 +/- 5.3%). The (CO2)-C-13 response increased in five out of seven subjects, but decreased in the other two, when moderate exercise was performed (bicycle ergometer, 50 W for 5 h). We conclude that the repeatability of the MTG test in healthy adults is low. The present results indicate that a solid and a liquid test meal, containing a similar amount of fats, give similar cumulative (CO2)-C-13 responses, and that stringent prolonged fasting during the test is unnecessary. Standardization of physical activity seems preferable, since the unequivocal effects of moderate exercise on the (CO2)-C-13 response were observed in the individuals studied.