Interlaboratory proficiency survey of high-density lipoprotein cholesterol measurement

Proficiency surveys of Seattle-area laboratories suggest only slight improvement in overall performance in high-density lipoprotein (HDL) measurement between 1978 and 1982, although the reported workload for HDL has increased by 15%. The mean interlaboratory SD was 64 mg/L (ranging from 34 for a pool averaging 299 mg/L to 136 for a pool averaging 886 mg of HDL cholesterol per liter) in 1982, compared with 79 mg/L (range 48-155) in 1978-79. Of the individual laboratory results in the current survey, 39% deviated by more than 50 mg/L from target values as compared with 37% in 1978-79. The discrepant values were primarily ascribable to method inaccuracy: only 30% of laboratories in 1982 reported results that averaged within 30 mg/L of target values (vs 50% in 1978). For within-run precision, 80% of laboratories in 1982 had SDs of less than 30 mg/L, vs 70% in 1978. The 1982 survey included a lyophilized serum prepared by spray freezing and bulk lyophilization (Hyland Omega), identical to the pools used in the College of American Pathologists Comprehensive Chemistry Survey, and five pools of frozen plasma. Interlaboratory variation and biases for the Omega pool were similar to those for the frozen pools.