Qualitative and quantitative aspects of the serological diagnosis of early syphilis.

The aim of the present study was to evaluate the use of various serological tests in the diagnosis of early syphilis. The Murex enzyme immunoassay (EIA) test was used for screening; the Venereal Diseases Research Laboratory (VDRL) test, the Treponema pallidum particle agglutination assay (TPPA) and the Mercia antitreponemal IgM EIA were used in all the patients with a positive screening test and in those with suspected syphilis or in known contacts. In 89 cases of primary syphilis, the Murex EIA screening test was positive in 67 (75%) patients, the Mercia IgM EIA in 80 (90%) cases, the VDRL in 60 (67%) cases and the TPPA in 85 (96%) cases. All the tests were positive in 68 patients with secondary syphilis. In 72 cases of early latent syphilis, the Murex EIA screening test was positive in 68 (94%) patients, the Mercia IgM EIA in 50 (69%) cases, the VDRL in 61 (85%) cases and the TPPA in 68 (94%) cases. The Mercia IgM EIA was the only test positive in four (6%) of these cases; these four patients were known contacts. Antibody titres in the VDRL and TPPA increased as the infection progressed.