Plasma post-heparin lipase activities in the HERITAGE family study: The reproducibility, gender differences, and associations with lipoprotein levels

Objectives: Examine the reproducibility of plasma lipid and lipoprotein mea surements in the HERITAGE Family study. Design and Methods: In a sample of 379 subjects (191 men and 188 women), re producibility was determined for lipids, lipoproteins (done on two occasion s) and post-heparin lipase assays using an Intracenter Quality Control stud y by generating split samples from an additional 60 subjects (35 men and 25 women), which were assayed in a blind fashion by the lipid core laboratory . Reproducibility was estimated using intraclass correlation coefficients ( ICC) for the selected variables. Analytical error (ANER) and coefficient of variation (CV) were also calculated. Day-to-day variation for 10 variables including plasma cholesterol and triglycerides (TG), HDL-cholesterol and i ts subfractions HDL2-cholesterol and HDL2-cholesterol, LDL-cholesterol and VLDL-cholesterol, as well as apoprotein (apo) A-I, apo B, and LDL-apo B wer e assessed. Results: In the HERITAGE study, all lipid and lipoprotein variables had ICC above 0.79. Plasma VLDL-cholesterol (31%) and TG (23%) levels, which are w ell known to be highly variable from one day to another, had CVs greater th an 20%. Other variables had CVs lower than 10% except for HDL2-cholesterol which reached 16%. In the intracenter reliability sub-study, the measuremen t errors were found to be low except for HDL2-cholesterol. For the lipases, the reproducibility of repeated samples was very high, with ICC over 0.95. The within-assay CV corresponded to 2.1 and 5.3% for hepatic lipase (HL) a nd lipoprotein lipase (LPL), respectively, whereas the between-assay CV rea ched 8-12% for HL and about 15% for LPL. Due to the complexity of these two assays, the results are considered to be quite satisfactory. Conclusions: The reproducibility of plasma lipid and lipoprotein measuremen ts, as well as of post-heparin lipase activities, is good in the multicente r HERITAGE Family Study. In addition, the well-documented gender difference in the plasma lipoprotein profile was confirmed in the present study, wome n having lower fasting triglyceride and LDL-cholesterol levels than men as well as reduced cholesterol/HDL-cholesterol and increased HDL2-cholesterol/ HDL2-cholesterol ratios compared to men. Results of the present study supp ort the notion that the higher LPL and low HL activities found in women com pared to men are important factors contributing to explain gender differenc e in the lipoprotein profile. However, additional factors not examined in t he present study are involved beyond the contribution of post-heparin lipas e to the sex dimorphism in plasma lipoprotein levels. Copyright (C) 1999 Th e Canadian Society of Clinical Chemists.