RESUMO
Background: LDL cholesterol is a known atherogenic factor and basis for risk classification of coronary heart disease. Reference method for measurement is beta-quantitation which is laborious and time consuming. The other method for measurement is direct homogenous assay which is costly so most laboratories use Friedwald’s formula for LDL measurement. Aim and Objectives: The aim of the study was to compare between calculated LDL by Friedwald’s formula and direct LDL by homogenous assay in fasting lipid profile samples. Material and Methods: We have taken data of 208 fasting lipid profile from past records after obtaining Institutional Ethics Committee permission. Patients with TG > 400 mg/dl were excluded from the study. Results: In our study, Pearson’s coefficient is 0.97 when TG < 200 mg/dl and Pearson’s coefficient is 0.95 when TG > 200 mg/dl. There is a less difference in patient’s risk classification by calculated LDL and direct LDL when TG < 200 mg/dl. Conclusion: Friedwald’s formula is a cost-effective method for measurement of LDL in comparison to homogenous assays. We can use calculated LDL when TG < 200 mg/dl without any risk of patient’s misclassification.
RESUMO
BACKGROUND: Low-density lipoprotein cholesterol (LDL-C) is a major risk factor in atherogenesis and coronary heart disease as well as a primary target of lipid-lowering therapy. LDL-C concentration by direct homogenous assay was compared with that of the Friedewald formula, which is widely used in spite of its limitations. METHODS: Between February and March 2002, we analyzed total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and LDL-C levels in 1, 161 subjects (601 men and 560 women). They were classified according to cutpoints of the National Cholesterol Education Program Adult Treatment Panel III guidelines. The LDL-C results by direct method and the Friedewald formula were compared according to the TG levels and their medical decision values. RESULTS: Overall results of the direct method (Y) and the Friedewald formula (X) were highly correlated (Y=0.90X+13.62, r=0.9225). LDL-C by the Friedewald formula, however, showed a tendency of underestimation at higher TG levels. The results of the direct method were significantly different compared with those of the Friedewald formula when TG > or =200 mg/dL (P or =200 mg/dL. Therefore, a direct determination method with better analytical performance is required. A fully automated homogenous assay seems to improve the determination of LDL-C, and may have a role in the diagnosis and management of hyperlipidemic patients.