THE C-13-MIXED TRIGLYCERIDE BREATH TEST IN HEALTHY-ADULTS - DETERMINANTS OF THE (13)CO2 RESPONSE

Defects in lipolysis due to pancreatic insufficiency can be diagnosed by the mixed triglyceride (MTG) (CO2)-C-13 breath test. However, the e ffects 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 dur ing the test; and (d) the effect of physical exercise during the test. Upon repeating the test in the same individual (test meal cream), rep eatability coefficients were large, with respect to either time to max imum 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 perio d (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 tha t obtained with bread and butter: 42.2 +/- 8.4% and 47.7 +/- 6.3% resp ectively. Fasting for 9 h during the test resulted in similar C-13 exp iration rates and cumulative C-13 expiration (43.4% +/- 7.2%) when com pared with consumption of an additional meal 3 h after the start of th e 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 exerc ise was performed (bicycle ergometer, 50 W for 5 h). We conclude that the repeatability of the MTG test in healthy adults is low. The presen t results indicate that a solid and a liquid test meal, containing a s imilar amount of fats, give similar cumulative (CO2)-C-13 responses, a nd that stringent prolonged fasting during the test is unnecessary. St andardization of physical activity seems preferable, since the unequiv ocal effects of moderate exercise on the (CO2)-C-13 response were obse rved in the individuals studied.