Performance characteristics of a recombinant enzymatic cycling assay for quantification of total homocysteine in serum or plasma

Background: Homocysteine is an amino acid that has been linked to an increased risk of coronary artery disease and stroke. A recombinant enzymatic cycling assay for homocysteine was evaluated using a Roche Modular Analytics P800 chemistry analyzer. Methods: Bound homocysteine is released by disulfide reduction and combined with serine to form L-cystathionine that is degraded by cystathionine β-lyase into homocysteine, pyruvate, and ammonia. Pyruvate is converted to lactate and the amount of NAD+ produced is directly proportional to the concentration of homocysteine. The limit of detection (LOD), linearity, imprecision, method comparison, reference interval and susceptibility to common interferences were assessed. Results: The limit of detection was 0.31 μmol/l. The method was linear from 1 to 100 μmol/l with a maximum deviation from the target concentration of