MEASUREMENTS OF PLASMA LDL CHOLESTEROL IN PATIENTS WITH DIABETES

OBJECTIVE - To assess the accuracy of plasma LDL cholesterol concentra tions estimated by the Friedewald formula and a direct immunoseparatio n method by comparison with a reference ultracentrifugation procedure in patients with diabetes. RESEARCH DESIGN AND METHODS - Fasting plasm a samples with triglyceride concentrations <4.5 mmol/l were collected from 100 patients with diabetes (28 type I and 72 type II) and LDL cho lesterol concentrations were compared by the three methods. RESULTS - LDL cholesterol values determined by the reference beta-quantitation p rocedure were highly correlated with both the Friedewald formula (r = 0.96) and a direct immunoseparation method (r = 0.92). Calculated (Fri edewald) LDL cholesterol coincided with the reference method with <10% error in 74% of the total diabetic group (82% of type I and 68% of ty pe II diabetic patients). However, agreement between the direct LDL ch olesterol and reference methods was significantly less (P = 0.02), wit h only 44% of patients having an error of <10% (52% of type I and 41% of type II diabetic patients). The direct immunoseparation method for LDL cholesterol showed a positive bias with increasing triglyceride co ncentrations, particularly for patients with type II diabetes. CONCLUS IONS - In the group of diabetic patients studied with plasma triglycer ide concentrations <4.5 mmol/l, the Friedewald formula provided an acc urate estimation of LDL cholesterol. The direct immunoseparation metho d significantly overestimated LDL cholesterol at triglyceride levels b etween 2 and 4.5 mmol/l.