Estimation of 14C-triolein assimilation from postprandial serum radioactivity of 14C

In an attempt to establish a test of lipid assimilation, based on the measurement of the postprandial serum radioactivity of 14C from ingested 14C-triolein, the activity of 14C was measured in serum samples, drawn 1,2,3,4,6 and 9 h after ingestion in 48 consecutive patients suspected of malassimilation. Simultaneously, faecal excretion of 14C was measured to estimate 14C-triolein assimilation (F-14C-Ass). F-14C-Ass served as reference of 14C-triolein assimilation. The sum of the 2- and 4-h serum concentration of 14C (S-(2 + 4)14C) was found to be most useful as an estimate of 14C-triolein assimilation, with regard to both the diagnostic value and applicability. At a level of 1.0% of dose/l serum, S-(2 + 4)14C correctly discriminated between normal and reduced 14C-triolein assimilation in 83% of the patients (95% confidence limits 70-93%). A significant correlation between 14C-triolein assimilation and S-(2 + 4)14C was found (r = 0.91, P less than 0.001). Since 14C-triolein assimilation correlates closely with the assimilation of dietary lipids, S-(2 + 4)14C seems to provide in a simple way sufficient information about lipid assimilation to be useful as a clinical test.