POOR APPLICABILITY OF THE FRIEDEWALD FORMULA IN THE ASSESSMENT OF SERUM LDL CHOLESTEROL FOR CLINICAL PURPOSES

Objective: To determine the accuracy of the estimation of serum low-de nsity lipoprotein (LDL) cholesterol concentration by the Friedewald fo rmula. Methods: Modifications of the calculation formula are presented on the basis of ultracentrifugal separation of serum high-density lip oprotein and LDL cholesterol in the specimens collected (n = 1215) in a nationwide health survey. Results: The formulas obtained from differ ent subject groups differed relatively little from each other. The acc uracy of the original Ffriedewald formula was poor; in about 36% of th e subjects the error was more than 5% compared with ultracentrifugally obtained results. By applying the currently recommended coronary hear t disease (CHD) risk categorizations, high proportions (5%-28%) of the subjects were classified into wrong CHD risk categories when LDL chol esterol was calculated with any of the formulas. At high serum triglyc eride levels, misclassifications were especially common. Conclusions: We conclude that even the most accurate LDL cholesterol calculation me thods should be used with caution while classifying subjects into cate gories of CHD risk. In hypertriglyceridemic subjects, the calculation formulas probably should not be used at all.