Analytical Performances of Sentinel and Vitros Direct LDL-C Assay Methods, and Classification of Patients with Hyperlipidemia Sentinel ve Vitros Direkt LDL-C Ölçüm Yöntemlerinin Analitik Performanslari ve Hiperlipidemi Siniflamasi

OBJECTIVE: A simple and accurate method is necessary to measure the LDL-C and sdLDL-C in serum. We aimed to evaluate the analytical performances of Sentinel and Vitros direct LDL-C (dLDL-C) assay methods, to compare LDL-C values of these direct methods with each other and with those values calculated by Friedewald formula, and to determine which lipid parameters could be more proper for classifi cation of patients with hyperlipidemia. METHODS: Analytical performances of direct methods were evaluated in 60 serum samples. LDL-C was determined in different 122 sera via two different direct methods and Friedewald formula. Sentinel sdLDL-C, Vitros sdLDL-C and other evaluated lipid parameters were estimated in additional 118 serum samples. RESULTS: Mean LDL-C concentrations for Sentinel dLDL-C, Vitros dLDL-C and Friedewald formula were 152±44 mg/dL, 146±45 mg/dL, 141±41 mg/dL, respectively (p<0.001). Signifi cant strong correlations were observed between Friedewald LDL-C and both Sentinel and Vitros dLDL-C (r=0.934, r=0.936, respectively). Although within-run imprecisions for direct methods were lower than 1.42%, total imprecisions for Sentinel and Vitros dLDL-C were lower than 1.73% and 4.8%, respectively. Sentinel and Vitros dLDL-C assay methods had 11% and 17.5% systematic error, respectively. While the lowest Friedewald LDL-C concentrations were observed in hypertriglyceridemic group, the lowest sdLDL-C values were obtained in normolipidemic group, although hyperlipidemia groups were based on Friedewald LDL-C. CONCLUSION: Vitros dLDL-C did not seem to be able to meet the performance criterion of NCEP ATP III for LDL-C, because its total imprecision was higher than 4%. Direct assay methods signifi cantly overestimated LDL-C values compared with Friedewald formula. Preference of the Sentinel direct LDL-C or sdLDL-C may be more useful for evaluation of patients with hyperlipidemia.