Validation of an immunoassay for measurement of plasma total homocysteine.

Hyperhomocysteinemia is an evolving cardiovascular risk factor. It is imperative that a simple, precise, and accurate assay be available in the clinical laboratory. The aim of this study was to evaluate an automated fluorescence polarization immunoassay for homocysteine. The assay had excellent precision at normal and high levels (intra-assay and interassay coefficients of variation < 5%). The method was linear from 0.24 to 50 mumol/L and displayed good correlation with a high-performance liquid chromatography (HPLC) method. There was no significant interference detectable in icteric and hyperlipidemic samples, but hemolysis resulted in a significant negative bias. While homocysteine levels were not increased in smokers, patients with renal failure had significantly higher levels compared with control subjects. This automated assay requires no sample preparation, displays excellent precision, shows good correlation with HPLC, and, thus, is favored over HPLC for use in the clinical laboratory. The main indications for measuring plasma homocysteine levels will be in the early diagnosis of cobalamin deficiency, patients with cardiovascular disease and few or no established risk factors, and patients with unexplained venous thromboembolic disease.