Investigation of isolated positive syphilis enzyme immunoassay (ICE Murex) results

This study was conducted to determine the significance of an isolated positive (where all other syphilis serology is negative) syphilis enzyme immunoassay (EIA) test (ICE syphilis: Murex Diagnostics) in a sexual health clinic population. There were significantly greater numbers of isolated positive syphilis EIA tests at Sydney Sexual Health Centre (SSHC) (22/5478) compared to lower risk populations; Southeastern Sydney antenatal clinics (1/11,560, P<0.01) and Sydney Children's Hospital (0/3550, P<0.01). We conducted a case control study comparing the cases at SSHC with two control groups drawn from the clinic population. A manual review of the case medical records searched for a history of suggested syphilis. Within the 22 cases, 32% had clinical grounds for suspecting that the EIA test signified syphilis. Men reporting homosexual contact in the past 12 months significantly distinguished cases from controls who tested negative for syphilis (OR=6.06). An isolated positive EIA test should prompt further investigation for syphilis, past or present.