Evolution of methods for measurement of HDL-cholesterol: From ultracentrifugation to homogeneous assays

Background. Adoption of automated homogeneous assays for HDL-cholesterol (H DL-C) is increasing, driven by the need of clinical laboratories to cope wi th increasing workloads while containing costs. However, performance charac teristics of homogeneous assays often differ in important aspects from thos e of the earlier precipitation methods. This review provides an overview of the new generation of homogeneous assays for HDL-C within the historical c ontext of the evolution of methods and the efforts to standardize measureme nts of the lipoproteins. Approach: This is a narrative review based on method evaluations conducted in the laboratories of the authors as well as on relevant publications, esp ecially comparative evaluation studies, from the literature. Publications c onsidered here have been collected by the authors over the past 30 years of involvement as methods for HDL-C made the transition from their early use in lipid research laboratories to clinical laboratories and the recent emer gence of homogeneous assays. Content. The presentation includes descriptions of methodologies, including homogeneous, precipitation, electrophoresis, and ultracentrifugation assay s. Reference methods and recommended approaches for assessing accuracy are described. Accuracy and imprecision are summarized in the context of the Na tional Cholesterol Education Program (NCEP) standards for analytical perfor mance. The effects of interfering substances and preanalytical sources of v ariation are presented. Summary: Homogeneous assays have been shown to be reasonably well suited fo r use in routine clinical laboratories, generally meeting the NCEP criteria for precision, accuracy, and total error. However, discrepant results comp ared with the reference methods have been observed with some of the assays, and the sources of discrepancies are not well characterized. Some homogene ous reagents have not been thoroughly evaluated. At least three of the reag ents have experienced successive adjustments in formulation; hence, the rea gents may not yet be fully optimized. For these reasons, the homogeneous as says cannot be confidently recommended for use in long-term clinical trials and other research applications without thorough validation. (C) 2001 Amer ican Association for Clinical Chemistry.