Agreement among four homocysteine assays and results in patients with coronary atherosclerosis and controls

Background: Hyperhomocysteinemia has been associated with coronary atherosc lerosis in many, but not all, prospective and retrospective studies. Some o n these inconsistencies may be attributed to methodological variabilities. Methods: In the present study, three newly commercially available assays an d one in-house HPLC assay for total homocysteine (tHcy) were utilized in 99 subjects with angiographically documented atherosclerosis and in 91 commun ity controls matched by age, gender, and smoking history. The in-house assa y, a modified Fortin and Genest HPLC method, was compared with the Bio-Rad HPLC assay, the Abbott IMx(R) fluorescence polarization immunoassay, and a Bio-Rad enzyme-linked immunoassay (EIA) microtiter method. Results: Correlation coefficient values between the inhouse HPLC assay and the Bio-Rad HPLC, the Abbott IMx, and the Bio-Rad EIA assays were 0.95, 0.9 6 and 0.90, respectively. Although tHcy concentrations were higher in cases compared with controls by all four methods, the difference reached statist ical significance only with the in-house HPLC procedure (median, 13.5 +/- 6 .7 mu mol/L in cases vs 10.9 +/- 4.8 mu mol/L in controls; P <0.01, adjusti ng for covariates), where it was an independent predictor of case or contro l status, along with hypertension, total cholesterol, and triglycerides. Th e tHcy distributions in cases and controls demonstrated significant overlap . The number of atherosclerotic major coronary vessels was associated with significantly higher tHcy (P <0.01 for trend) in all four methods. Conclusions: The three commercial assays for tHcy differed in analytical an d clinical performance. Analytically, the Abbott IMx method showed the best comparability with the in-house assay, but clinically, the three commercia l methods were similar and did not distinguish cases from controls. (C) 200 0 American Association for Clinical Chemistry.