title: Optimization of routine plasma homocysteine monitoring.
abstract: 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 Hcy 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 (r2 = 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 Hcy 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.
authors.affiliation: Department of Haematology, St. James's Hospital, Dublin, Ireland. nutrition@stjames.ie
authors.forename: S D
authors.initials: SD
authors.lastname: O'Broin
authors.forename: B P
authors.initials: BP
authors.lastname: Kelleher
authors.forename: J
authors.initials: J
authors.lastname: McPartlin
authors.forename: P
authors.initials: P
authors.lastname: O'Gorman
authors.forename: M
authors.initials: M
authors.lastname: Browne
authors.forename: B
authors.initials: B
authors.lastname: White
authors.forename: O P
authors.initials: OP
authors.lastname: Smith
mesh_terms: D016903:Drug Monitoring / Q000379:methods*; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D012680:Sensitivity and Specificity
chemical_list: D006710:Homocysteine