Multicenter analytical evaluation of an automated immunoassay for total plasma homocysteine

A fully automated immunoassay for total plasma homocysteine assay was evalu ated at four centers. To measure total homocysteine, oxidized forms of homo cysteine in serum and plasma were reduced by dithiothreitol and assayed by a competitive fluorescence polarization technique. The assay had within-run precision from 0.9 to 3.0% and total precision from 2.8 to 4.1% for contro l materials with homocysteine concentrations of approximately 7, 12.5, and 25 mu mol/l, a sensitivity of 0.35 mu mol/L, good parallelism upon dilution , and analytical recovery ranging from 97.4 to 103.8%. The immunoassay corr elated with four different HPLC assays for homocysteine, yielding a slope o f 0.98, an intercept of -0.19 mu mol/L, and a correlation coefficient of 0. 966 for 440 paired samples. The reference range, determined with plasma sam ples from 609 males and 600 females, yielded a mean of 9.17+/-2.86 mu mol/L , with a central 95% range of 4.78-15.43 mu mol/L. The immunoassay is a sui table alternative to HPLC and may be useful in screening persons with high risk of coronary artery disease.