Comparison of four direct homogeneous methods for the measurement of low-density lipoprotein cholesterol.

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.