Diagnostic Performance of a Rapid Syphilis Test Among Pregnant Women in Peru

Background: Maternal and congenital syphilis are pressing concerns in Latin America, with consequences ranging from newborn mental retardation to perinatal death. Widespread, accurate screening and timely penicillin treatment can help. Simple, affordable, point of care rapid syphilis tests (RSTs) promise to improve screening coverage among pregnant women.

Methods: From September 2009 to November 2010, Project CISNE implemented the SD Bioline Syphilis 3.0 RST into two health networks, offering the test to pregnant women aged 16 55 who attended antenatal care, delivery/postpartum, and abortion services. The performance analysis compared Bioline RST results with reference standards TPPA and RPR+TPPA, adjusting estimates according to sampling realities.

Results: 17,147 rapid syphilis tests were performed in the field and 11,169 were screened in the central laboratory. Syphilis prevalence was 1.05% (0.73% adjusted) according to the gold standard vs. 0.90% according to the field RST. The Bioline RST displayed an unadjusted sensitivity of 91.0% (95% CI 86.4 95.0) and specificity of 99.1% (98.1 99.6) compared to TPPA, and an unadjusted sensitivity of 91.5% (84.8 95.8) and specificity of 99.6% (99.4 99.7) compared to RPR+TPPA. When adjusted, overall sensitivity and specificity compared to RPR+TPPA were 86.5% (78.8 92.0) and 99.7% (99.6 99.8), respectively. The Bioline RST yielded more false positive than false negative results due to the observed low prevalence.

Discussion: Despite limitations, this study displays the field RST to be reliable, reproducible, as valid as previous studies, and diagnostically apt for implementation in maternal care services in Peru.