Optimization of routine plasma homocysteine monitoring.

An elevated plasma homocysteine (Hcy) level is now considered to be an important risk factor in arterial and venous thromboembolic events. As a result of this relatively recent finding, there has been a dramatic increase in the number of requests for Hey measurement. In our laboratory, this demand has been met by employing an automated immunoassay and improving the pre-analytical handling of blood samples. An automated fluorescent polarization immunoassay (FPIA) gave similar results to a reference high-pressure chromatographic (HPLC) method (r(2) = 0.98, enzyme immunoassay = 0.998 HPLC - 0.3) and excellent between-run reproducibility (coefficient of variation < 3%). The new assay also required less specialized technical input, and improved the sample throughput two-fold. Pre-analytical stability of plasma Hey concentrations in blood samples is crucial to the accuracy of Hcy monitoring. This stability was improved 10-fold by adopting the anticoagulant acidic citrate instead of ethylenediamine tetraacetic acid for Hcy screening by FPIA. Acidic citrate dramatically inhibits time-related plasma contamination by red-cell Hcy, resulting in improved accuracy and a reduced number of 'spoiled' specimen discards. Blood Coagul Fibrinolysis 11:367-369 (C) 2000 Lippincott Williams & Wilkins.