ASSESSMENT OF INTERLABORATORY PERFORMANCE IN EXTERNAL PROFICIENCY TESTING PROGRAMS WITH A DIRECT HDL-CHOLESTEROL ASSAY

Direct assays for the determination of HDL-cholesterol (HDL-C) have re cently become available, The methods are precise, require small sample volume, and appear to be less affected by increased triglycerides tha n traditional precipitation methods. In this study, we describe the in ter- and intralaboratory variability of the Boehringer Mannheim Corpor ation direct HDL-C assay and its performance in external proficiency t esting surveys. A comparison study among three laboratories, using dif ferent analyzers and 85 serum specimens, showed a correlation coeffici ent (r) of 0.99. The direct HDL-C assay also showed good agreement wit h the ultracentrifugation-dextran sulfate-Mg2+ method (r = 0.98) and t he Cholesterol Reference Method Laboratory Network-Designated Comparis on Method (a = 0.98x + 4.75 mg/L, r = 0.98). Total error at medical de cision levels ranged from -0.8% to +1.1%. Furthermore, this assay perf ormed adequately in the College of American Pathologists and the ALERT (R) surveys as well as the CDC Lipid Standardization Program and met a ll performance criteria of regulatory agencies.