Variability in cholesterol measurements: comparison of calculated and direct LDL cholesterol determinations.
Calculated low-density lipoprotein cholesterol (LDL-C) concentrations determined from the Friedewald equation have a large intraindividual CV, in part because the calculation incorporates the variability of cholesterol, high-density lipoprotein cholesterol (HDL-C), and triglyceride measurements. We studied whether a new assay that measures LDL-C directly will reduce this variability and reduce the need for averaging serial specimens. Four blood samples were obtained 1 week apart from 35 mildly hypercholesterolemic subjects and analyzed for total cholesterol, triglycerides, and HDL-C. LDL-C was calculated by the Friedewald equation, and was also measured directly with a commercially available direct LDL-C assay. The intraindividual CV for the direct and calculated LDL-C assays were similar [CV of direct LDL-C assay (mean +/- SE): 6.8 +/- 0.5% vs calculated LDL-C: 7.3 +/- 0.6%; difference 0.44%, 95% confidence interval: -0.7-1.5%]. For both assays, at least two blood tests were required from each subject to reduce total variability of LDL-C to less than or equal to 5%. We conclude that the direct LDL-C assay did not reduce the variability in LDL-C compared with the conventional LDL-C calculation. However, it may have a specific role in lipid disorder evaluation and (or) monitoring when triglycerides are increased or the LDL-C value alone is needed.
Schectman
G
G
Division of General Internal Medicine, Department of Medicine, Medical College of Wisconsin, Milwaukee 53221, USA.gschect@post.its.mcw.edu
Patsches
M
M
Sasse
E A
EA
D000328:Adult; D000368:Aged; D002784:Cholesterol / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood*; D007118:Immunoassay / Q000706:statistics & numerical data; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D014280:Triglycerides / Q000097:blood
D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D014280:Triglycerides; D002784:Cholesterol