Laboratory measurement of lipid and lipoprotein risk factors.

Accuracy in measurement of serum cholesterol and the other lipid risk factors is essential for reliable patient classification within the context of newly implemented national coronary heart disease intervention programs utilizing uniform cutpoints. This requires agreement or traceability of laboratory methods to national reference systems, which provided the accuracy base for the population studies from which the cutpoints are derived. Adhering to accepted guidelines for patient preparation, blood collection and processing will minimize preanalytical variability. Standardization of the lipid/lipoprotein assays is the next essential step. The assay technology for cholesterol measurement is reasonably mature, although still not perfected; recent activities have focused primarily on achieving traceability of field methods through improving access to the accuracy base, the National Reference System for Cholesterol and developing better (commutable) reference materials. A major hindrance to standardization has been matrix interactions; alterations in reference materials from their preparation which change the measurement characteristics, necessitating the use of fresh specimens in accuracy studies. Considering the importance of LDL cholesterol which is the primary decision parameter in the new clinical guidelines; methodology for routine laboratory quantification is substantially lacking, the usual routine approach still involving estimation. Efforts to develop a reference system for LDL are just beginning. Field methods for HDL cholesterol are reasonably reliable but with some inter-method differences. Agreement on and access to a Reference Method is needed. Accuracy in triglyceride measurement is less important compared to the other risk factors. Convenient methods allowing correction for the free glycerol blank and ready access to a Reference Method are needed.