INTRODUCTION:
Syphilis is caused by Treponema pallidum pallidum (Tp) and, often, the diagnosis is by non treponemal (RPR/VDRL) or treponemal (TPHA/FTA-Abs) serological methods. Recently, Polymerase chain reaction (PCR ) technique has been suggested in the diagnosis of syphilis. Among possible target genes, Tp47 exhibited a better performance in pediatric population.
OBJECTIVE:
Our objective is to study if the detection of Tp47 gene by PCR can contribute to the diagnosis of syphilis and monitor treatment response in the pediatric population assisted in our service.
PATIENTS AND METHODS:
Samples (whole blood and lesion ´swabs) were collected during the development of a prospective, multicenter cohort study during the period of 2019-2021. Inclusion criteria were: Child with a non-sexual transmission- acquired syphilis diagnosis, adults’ co-habitant of child with acquired syphilis. Exclusion criteria: having received at least one dose of penicillin treatment, patient with physical or sociopsychologic indicator of sexual abuse. Samples were obtain along with serological determination at diagnosis, immediately and 12 months after treatment. Samples were processed for DNA extraction using commercial columns and Tp detection by conventional PCR for Tp47 gene. We assessed the performance of the test using the TPHA results as gold standard for the determination of the sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV). Analyses were performed with EPIDAT 3.1 software.
RESULTS:
Samples of 21 patients (12 children, 9 adults)were assessed. The analysis of the technique showed a variable sensitivity according to the type of sample (61,3% swab-66,7%whole blood), while specificity remained at 100% and 80% respectively. Currently postreatment-PCR results are under study for monitoring syphilis treatment response.
CONCLUSION:
PCR for TP47 is a robust technique with high specificity and complementary to serological methods in diagnosis and a possible biomarker of treatment response
