DIRECT ASSAY OF LDL CHOLESTEROL - COMPARING MEASUREMENT AND CALCULATION

Low-density lipoprotein (LDL) cholesterol is a critical lipid subfract ion because it is linked directly with the risk of coronary heart dise ase (CHD). Current approaches to diagnosing and monitoring CHD emphasi ze the significance of accurate, precise LDL values. Due to the inhere nt complexity of measuring LDL by the reference method, ultracentrifug ation, it usually is estimated by a calculation that uses measured val ues for total cholesterol, high-density lipoprotein (HDL) cholesterol and triglycerides. Calculated LDL (CLDL) results may be inaccurate, es pecially if a patient triglyceride level is elevated, and it requires a specimen from a patient who has fasted. New assays allow for the dir ect measurement of LDL (DLDL) analogous to assays for HDL and do not r equire the patient to fast. While CLDL typically compares well with ul tracentrifugation and DLDL, it may provide a result that is different in some instances; that difference may have clinical significance. A m ethod comparison study of CLDL and DLDL resulted in the following line ar regression equation: DLDL = 1.067 CLDL + 1.597, r = 0.974, n = 36.