A rapid and precise immunoassay for quantification of total homocystei
ne in blood samples is presented. The method avoids the use of radiois
otopes and chromatographic separations and relies on enzymatic convers
ion of homocysteine to S-adenosyl-L-homocysteine, followed by quantifi
cation of S-adenosyl-L-homocysteine by an enzyme-linked immunoassay in
microtiter format. The within-and between-assay imprecision is <6% an
d 8%, respectively, and results by the method show good correlation wi
th those by HPLC. Including controls and calibrators in duplicates, 82
samples can be analyzed within 2.5 h. The procedure can be fully auto
mated.