Sensitivity and specificity of epidemiological criteria for the case definition of congenital syphilis in a retrospective cohort in BrazilSensibilidad y especificidad de los criterios epidemiológicos para la definición de los casos de sífilis congénita en una cohorte retrospectiva en Brasil

Abstract

To assess the sensitivity and specificity of the modified criteria for case definition of congenital syphilis implemented in 2017, which excluded treatment of the sexual partner as a necessary condition for adequate maternal treatment. This retrospective cohort study involved epidemiological monitoring of 503 children born in 2018 and living in Porto Alegre, Brazil: 412, including miscarriages and stillbirths, had been reported as congenital syphilis cases; 91, who had been exposed to syphilis during pregnancy, were no longer considered cases after partner treatment was excluded as a criterion for adequate maternal treatment. The study involved observation of treatment at birth, laboratory follow-up with non-treponemal tests up to age 18 months or treponemal tests after age 18 months, and symptom-based screening for cohort closure. A total of 286 cases and 126 non-cases were identified using the criteria for reportable cases. Among those exposed but who did not meet the criteria for reportable cases, three cases and 88 non-cases were identified (p < 0.001). Considering the current case definition of congenital syphilis for reporting purposes, the sensitivity was 98.9% (95%CI: 97.0 to 99.7), and the specificity, 41.0% (95%CI: 34.4 to 48.0). The monitoring strategy for case closure had a sensitivity of 69.4% (95%CI: 64.7 to 73.8) and a specificity of 96.7% (95%CI: 90.7 to 99.3). The current case definition of congenital syphilis case for reporting purposes proved sensitive, but less specific. We suggest that it be reviewed in light of the possibility of missing true-positive diagnoses.