Study of homocysteine concentration in coronary heart disease patients and comparison of two determination methods

Abstract

Introduction: Elevated total homocysteine (tHCY) is a known risk factor for atherosclerotic vascular disease, but the mechanism is not well understood. The study was designed to estimate tHCY concentration and other risk factors in coronary heart disease (CHD) males, evaluating two different methods for tHCY measurement: gas chromatography-mass spectrometry (GC-MS) method and competitive immunoassay method.

Materials and methods: Fifty men, mean age 53.9 years with CHD and a body mass index (BMI) >25.0, were examined for tHCY concentrations, lipids, blood glucose, uric acid, complete blood picture and erythrocyte sedimentation rate and high-sensitive C-reactive protein (hsCRP). Biochemical and hematological indices were determined by routine methods, hsCRP--by immunometric chemiluminescence method, and tHCY--by two different methods: a gas chromatographic method, using GC-MS and a competitive immunoassay method on an Immulite device.

Results: The mean values of the lipids showed moderate dyslipidemia while the other parameters were within reference range. Mean BMI was 28.5 +/- 0.42. Values of tHCY determined by the immunoassay method were 13.2 +/- 0.95 micromol/l, and determined by GC-MS - 14.6 +/- 1.09 micromol/l. We found a linear agreement between the DPC and GC-MS sets of measurements (r = 0.87, p < or = 0.001). The median tHCY concentrations measured by immunoassay were lower than those measured with GC-MS, but differences were insignificant. An agreement between the competitive immunoassay and the GC-MS method evaluated by the Bland and Altman method was found. tHCY was >15 micromol/l in 12 patients as determined by the competitive immunoassay, and in 15 patients by the GC-MS method. tHCY levels were between 10 and 15 micromol/l in 24 patients by the immunoassay and in 29 patients by the GC-MS method. Twenty-four percent of the patients with CHD have an 'increased risk' with tHCY >15 micromol/l, and 48% are in the 'gray zone' with tHCY levels between 10 and 15 micromol/l.

Conclusions: 40.8% of the studied patients had increased tHCY levels, not associated with the other lipid and nonlipid risk factors. The closest conformity between GC-MS and immunoassay methods was observed for serum tHCY concentrations. The between-method comparison reveals that the above-mentioned methods can be used interchangeably.