Enzymatic determination of triglycerides in human and baboon serum triglycerides

Human and baboon serum samples were enzymatically analyzed for free glycerol and total triglyceride (as glycerol) with a discrete analyzer (Abbott Laboratories' ABA-100). Total baboon serum triglycerides (x), determined enzymatically without correction for free glycerol, compared with the semiautomated Dade-25 method (y) on the Technicon AutoAnalyzer I yielded a regression equation of y = 0.787 x - 0.068 mmol/liter (r = 0.944, standard error of estimate = 0.150). With a correction of the enzymatic method for free glycerol, the regression equation was y = 0.97 x + 0.002 mmol/liter (r = 0.988, standard error of estimate = 0.069). Of the total glycerol (triglyceride glycerol and free glycerol) 32% (SD, 18) was free glycerol for baboon sera, 10% (SD, 4) for human sera, 12 to 85% for various quality-control sera. The correlation between free glycerol and total triglycerides in baboon serum was poor (r = 0.190). These results suggest that for accurate triglyceride determinations the free glycerol concentration must be estimated independently for each sample, and that a standard correction for free glycerol would result in large errors in reported triglyceride concentration, especially for baboon sera and pooled quality-control sera. Initial determination of free glycerol followed by manual addition of the lipase permitted a sequential triglyceride analysis of a single serum aliquot. This procedure compared to separate determination of free and total glycerol halves reagent costs and decreases analysis time. An accessory of the ABA-100 allows correction for occasional turbidity or air bubbles formed during mixing of the sample and reagents.