Comparison of enzyme-linked immunosorbent assay with enzyme-linked fluorescence assay with automated readers for detection of rubella virus antibody and herpes simplex virus.

The enzyme-linked immunosorbent assay (ELISA) was compared with the enzyme-linked fluorescence assay (ELFA) for the detection of rubella antibody and herpes simplex virus antigen. Test parameters, specimens, antigen or antibody, and conjugates for the two types of assays were identical except that p-nitrophenyl phosphate was used as the substrate for the ELISA and 4-methylumbelliferyl phosphate was used as the substrate for ELFA. Automated readers were used for both assays. Antibody titers and sensitivity of antigen detection were quite similar for ELISA and ELFA. ELFA for rubella antibody, however, could be conducted with less antigen or shorter substrate incubation time (5 min for ELFA versus 30 min for ELISA). For herpes simplex virus antigen detection, ELFA could also be read after a shorter substrate incubation time (15 min for ELFA versus 30 min for ELISA). Clear polystyrene microtiter plates routinely used for ELISA could be used for ELFA, but clear polyvinyl chloride plates had high background fluorescence. Black polystyrene and polyvinyl chloride plates gave lower background fluorescence than did clear plates. ELFA is of particular value as a substitute for ELISAs in which long substrate incubations are required or antigens of only low titer are available.