Serological tests for syphilis in Saudi Arabia.

A total of 6684 sera were initially screened for syphilis by the Venereal Disease Research Laboratory (VDRL) test and the Treponema pallidum haemagglutination assay (TPHA). Reactive sera from either or both these tests were tested for confirmation by the fluorescent treponemal antibody-absorbed (FTA-ABS) test. VDRL biological false positive reactors were detected in 0.5% of the total sera examined, with 0.4% and 0.8%, respectively, obtained in pregnant women and blood donors. Eight sera (0.1%) were found to be positive in the TPHA test alone. An overall positivity of 2.7% for syphilis was detected, with a 0.85% positivity in antenatal patients. Infection with T pallidum seemed to be more common in men than in women (1.6:1) and predominated in the age group 20-39 years. Serological testing of sera from 26 mother and infant pairs allowed one case of congenital syphilis to be detected by FTA-ABS (IgM) and identified VDRL biological false positivity in seven infants.