Evaluation of the microenzyme-linked immunosorbent assay with Treponema pallidum antigen.

Whole-cell sonicates of Treponema pallidum, Nichols strain, were evaluated in an enzyme-linked immunosorbent assay (Elisa) for syphilis, and results were read in a Dynatek Microelisa Reader. The antigen was evaluated with sera from patients with syphilis, persons presumed normal, and biological false-positives. Two hundred and ninety-seven sera were tested by the ELISA with T. pallidum antigens, the Venereal Disease Research Laboratory (VDRL) slide test, the fluorescent treponemal antibody absorption (FTA-Abs) test, and the microhemagglutination assay for T. pallidum antibodies (MHA-TP). The results of all of the tests were compared. The ELISA, with 89.3% sensitivity, was less sensitive than the VDRL (93.3%) and FTA-Abs (100.0%) tests but more sensitive than the MHA-TP (76.0%). THe ELISA was considerably more sensitive in primary syphilis than the MHA-TP. Specificity was as follows: ELISA, 98.5%; FTA-Abs test, 97.8%; MHA-TP, 98.2%; and VDRL test, 92.7%. The ELISA has good potential as a confirmatory test in the serodiagnosis of syphilis.