[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

Objective: 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.

Methods: 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.

Results: 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).

Conclusion: 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.