Analytical and Clinical Performance of a Detergent-based Homogeneous LDL-Cholesterol Assay: A Multicenter Evaluation

Abstract

Background: LDL-cholesterol (LDL-C) concentrations currently are determined in most clinical laboratories using the Friedewald calculation. This approach has several limitations and may not always meet the current total error recommendation in LDL-C measurement of ≤12% established by the National Cholesterol Education Program. Methods: In a multicenter study, we evaluated the analytical and clinical performance of a homogeneous LDL-C assay (LDL-CRoche; Roche Diagnostics, Indianapolis, IN) in a comparison with a β-quantification method. Results: This direct assay correlated highly with a β-quantification method (r = 0.968; y = 1.037x − 95.8 mg/L; n = 355; 95% confidence intervals, 1.011–1.063 for the slope and −129.5 to 62.0 mg/L for the y-intercept) and met the current total error requirement. The assay was not affected significantly by concentrations of hemoglobin up to 6000 mg/L or bilirubin up to 500 mg/L. However, a negative bias of 10% was seen when triglyceride concentrations exceeded 10 000 mg/L. At the medical decision cut-point range, the LDL-CRoche assay showed positive predictive values of 91–100% and negative predictive values of 80–99%. Furthermore, the clinical utility of the assay seemed unaffected in samples obtained postprandially. Conclusions: The homogeneous LDL-CRoche assay meets the currently established analytical performance goals and may be useful for the diagnosis and management of hyperlipidemic patients.

Does Friedewald Formula Underestimate the Risk of Ischemic Heart Disease?

“…Strategies for treatment of lipid abnormalities are primarily based on LDL-C concentration. Therefore, LDL-C must be [8,11]. Some authors have demonstrated that the formula should not be used in certain groups of patients with diabetes, liver and renal dysfunction even with TG levels \4.52 mmol/l [12][13][14].…”

“…Even in the presence of small amounts of chylomicrons or abnormal lipoproteins, the formula gives rise to falsely low LDL cholesterol values. As well, the homogenous Roche method we have used has some limitations [6] although it has been reviewed by Nauck et al [11] to be precise and acceptably accurate. It gives an improvement in the measurement of LDL-C in samples with high TG and may assist better in classification of patients at risk categories for cardiovascular diseases than Friedewald's equation.…”

“…All patients who had TGs more than 400 mg/dl were excluded from the study. High-density lipoprotein cholesterol (HDL-C) was measured using a homogeneous assay without precipitation (Roche Diagnostics GmbH, Mannheim, Germany) [11]. Friedewald formula was used to obtain calculated LDL cholesterol values (C-LDL = TC -HDL-C -TG/5).…”

“…The principle of D-LDL determination is as follows: At pH 6.75 in the presence of magnesium ions and a sugar compound the enzymatic reaction for cholesterol in very low-density lipoprotein (VLDL) and chylomicrons is markedly reduced. Selective micellary solublization of LDL cholesterol by a non ionic detergent enables its measurement by a conventional enzymatic reaction with cholesterol esterase, cholesterol oxidase and peroxidase (Roche Diagnostics GmbH, Mannheim, Germany) [6,11]. This direct homogeneous assay has been shown to meet current NCEP criteria for precision (CV \ 4 %), accuracy (bias \ 4 %) versus reference method and for total analytical error (\12 %) [4,11].…”

“…Selective micellary solublization of LDL cholesterol by a non ionic detergent enables its measurement by a conventional enzymatic reaction with cholesterol esterase, cholesterol oxidase and peroxidase (Roche Diagnostics GmbH, Mannheim, Germany) [6,11]. This direct homogeneous assay has been shown to meet current NCEP criteria for precision (CV \ 4 %), accuracy (bias \ 4 %) versus reference method and for total analytical error (\12 %) [4,11]. Within run CVs for direct LDL-C were 0.9 % at 96.9 mg/dl and 1.3 % at 237 mg/dl and the total CVs were 1.9 % at 56.…”