Analytical performance and clinical efficacy of three routine procedures for LDL cholesterol measurement compared with the ultracentrifugation-dextran sulfate-Mg(2+) method.
The diagnosis and management of adults with hypercholesterolemia in the US are largely based on low-density lipoprotein cholesterol (LDL-C) concentration. In order to classify someone correctly into the National Cholesterol Education Program cut-points, LDL-C must be measured with a total error of </=12%. We examined simultaneously the analytical and clinical performance of two homogeneous LDL-C assays (LDL-C(RD), Roche Diagnostics and LDL-C(GZ), Genzyme) and the Friedewald calculation (LDL-C(Fried)). These assays correlated highly with the ultracentrifugation-dextran sulfate-Mg(2+) method (LDL-C(RD): r=0.962, y=1.029x-0.48 mmol/l, n=134; LDL-C(GZ): r=0.961, y=0.986x-0.12 mmol/l, n=134; LDL-C(Fried): r=0.960, y=1.017x-0.18 mmol/l, n=115). The total error requirement was met by the LDL-C(GZ) assay at all clinical decision cut-points, whereas the LDL-C(RD) assay met this requirement only at LDL-C concentrations of 4.92 mmol/l. The LDL-C(Fried) failed to meet the total error requirement, because the compounded imprecision of the three independent tests required for this calculation was high. Both, the LDL-C(GZ) and the LDL-C(RD) assays appeared to be only slightly affected by increasing triglycerides. At the medical decision cut-point range, the LDL-C(RD), LDL-C(GZ) and LDL-C(Fried) assays showed positive predictive values of 89-100, 85-100 and 83-99%, respectively, and negative predictive values of 52-98, 77-98 and 68-98%, respectively. The homogeneous assays provide clinical laboratories with the means to measure LDL-C in hypertriglyceridemic samples and could have a role in the diagnosis and management of hyperlipidemic patients.
Nauck
M
M
Departments of Laboratory Medicine and Pathology, Children's Hospital and Harvard Medical School, Boston, MA, USA.
Rifai
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N
D000328:Adult; D002784:Cholesterol / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D002914:Chylomicrons / Q000097:blood; D016264:Dextran Sulfate; D005215:Fasting; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood* / Q000175:diagnosis; D015228:Hypertriglyceridemia / Q000097:blood / Q000175:diagnosis; D008274:Magnesium; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D012044:Regression Analysis; D015203:Reproducibility of Results; D014280:Triglycerides / Q000097:blood; D014461:Ultracentrifugation / Q000379:methods
D008078:Cholesterol, LDL; D002914:Chylomicrons; D011933:Reagent Kits, Diagnostic; D014280:Triglycerides; D016264:Dextran Sulfate; D002784:Cholesterol; D008274:Magnesium