Congenital syphilis in children under 2 years of age surveillance evaluation in a hospital, Chiangmai Province, Thailand during 2020–2022

Abstract

Introduction: Since 2015, the prevalence of congenital syphilis has been increasing in Thailand. In Chiang Mai, the prevalence rates were 1.95, 1.08, and 1.15 per thousand live births in 2020, 2021, and 2022, respectively. An evaluation of the congenital syphilis surveillance system at a hospital was conducted to assess both its quantitative and qualitative attributes, with the aim of enhancing the system’s effectiveness.

Method: A cross-sectional study was conducted from 2020 to 2022, assessing the system’s quantitative and qualitative attributes based on cases identified with ICD–10 A50 (congenital syphilis) and other diseases presenting with similar symptoms. A stratified random sampling technique was employed for the quantitative analysis, while hospital staff were interviewed for the qualitative assessment to evaluate the surveillance system.

Results: Of the 297 cases examined, 30 were diagnosed with congenital syphilis, with only 11 of these cases being registered in the 506 surveillance system. The sensitivity of the system was 25.64%, and the Positive Predictive Value (PPV) was 45.83%. Timeliness was 100%, and data quality, including completeness and accuracy, was 100% and 75%, respectively. However, the system lacked representativeness. Regarding the qualitative analysis, the system was found to be simple, with a user-friendly computer program in place. Surveillance system guidelines were available, and hospital staff could easily substitute for one another in carrying out surveillance duties, supported by a handbook. Flexibility and stability were deemed satisfactory. Hospital staff recognized the importance of the congenital syphilis surveillance system; however, its usage was low among clinicians and other stakeholders, as congenital syphilis was perceived to be a less urgent public health issue compared to other diseases.

Conclusions: The evaluation of the congenital syphilis surveillance system at the hospital revealed inadequate effectiveness, with low sensitivity and PPV. The primary cause of low sensitivity was the Single Side Band (SSB) program, the hospital’s own data collection system, which only collected diagnostic data from outpatient cases 1–2 days before entry into the system. Consequently, cases were missed if patients did not return for follow-up at the same hospital or missed appointments, resulting in incomplete data capture in the 506 surveillance system.