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Comparison of Four Direct Homogeneous Methods for the Measurement of Low-Density Lipoprotein Cholesterol by Koji Yamada, Naoki Tsuji, Tomoko Fujita, Maki Tanaka, Kageaki Kuribasyashi, Daisuke Kobayashi, Naoki Watanabe

Background: The primary lipoprotein risk factor is low-density lipoprotein cholesterol (LDL-C), and medication is targeted at lowering LDL-C values. To clarify the usefulness of direct homogeneous assays for LDL-C measurement, we compared the values obtained by various reagents to those obtained by the Friedewald equation and analyzed different reactivity to IDL/VLDL and LDL.
Methods: Serum samples were collected from 55 patients with hypercholesterolemia. The LDL-C concentrations were determined by four direct homogeneous assays using reagent A (Kyowa Medex), B (Sekisui Medical), C (Denka Seiken), and D (Sysmex), which are commercially available.
Results: Significant correlation was observed in LDL-C values obtained by the homogeneous assays and the Friedewald equation. However, there were two discrepancies in reagents B and C, respectively. These assays showed 40 % and 55 % lower LDL-C values than those calculated by the Friedewald equation, respectively. Reactivity to the IDL fraction in reagents B and C was lower than in reagents A and D.
Conclusions: Direct homogeneous assays for LDL-C are suitable for routine laboratory examination. However, it was shown that attention should be given to the different reactivity to IDL and LDL among reagents in some clinical samples.

DOI: Clin. Lab. 2010;56:327-333