Rapid homogeneous enzyme immunoassay of plasma protein C

A homogeneous EIA (H-EIA) technique for plasma protein C antigen using horseradish peroxidase (HRP) was developed. This technique, which avoids the bound/free separation and washing procedures and shortens the assay time to 30 min, has several advantages over the conventional EIA technique. The measurement was valid for 1.0% to 200% of the plasma protein C level and had intraassay coefficients of variation of 2.3-11.0%. The results of this assay correlated well with those of conventional sandwich EIA (x) with a regression equation of y = 0.782x + 6.637, r = 0.911 (n = 59). This method, which may also be applicable to automatic assay systems, is considered to be suited for clinical laboratory use.