Chemiluminescent enzyme immunoassay for alpha-fetoprotein using beta-D-galactosidase as label and 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside as substrate.

We developed a sensitive chemiluminescent sandwich-type enzyme immunoassay (CL-EIA) of alpha-fetoprotein (AFP) using beta-D-galactosidase (beta-gal) as a label and 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside as a substrate. The CL-EIA for AFP was performed using two monoclonal antibodies, one antibody is labelled with beta-gal, the other is coated onto the inside surface of a polystyrene tube. The detection limit for AFP was 0.5 ng/mL, equivalent to 10 pg/assay tube. The coefficient of variation for within and between assay imprecision were 2.0%-4.9% (n = 10) and 4.4%-9.8% (n = 5), respectively. AFP values in serum determined by this method correlated well with those obtained by radioimmunoassay (n = 26, r = 0.99). This sensitive AFP assay can be performed within 4 h and can be used as a routine assay in clinical diagnosis.