Performance of a direct LDL-cholesterol method compared to beta quantification

Abstract

Low-density lipoprotein cholesterol is currently estimated by clinical laboratories using the Friedewald formula which requires fasting specimens and is subject to error with increasing triglyceride levels. We describe a rapid method for isolating low-density lipoproteins by immunoseparation for subsequent measurement of cholesterol by enzymatic assay. The Direct LDL™Immunoseparation Reagent meets current guidelines for precision with intra-assay and interassay coefficients of variation of <3%. The results are highly correlated to the beta quantification reference method (r=0.980). The results are generally not affected by increasing levels of triglycerides or high-density lipoprotein cholesterol and patient fasting is not required for accurate analysis. The Direct LDL Immunoseparation Reagent overcomes limitations of the Friedewald formula and appears to be suitable for accurate quantitation of low-density lipoprotein cholesterol in the routine laboratory.