Frequent Oropharyngeal Detection of Treponema pallidum DNA in Patients with Syphilis: A Cross-Sectional Study of Three Anatomical Sampling Sites.

Objectives

To compare Treponema pallidum (TP) PCR positivity across anatomical sites and assess whether oropharyngeal sampling warrants prospective evaluation as an adjunct to serology in suspected early syphilis without suitable lesion material.

Methods

Retrospective cross-sectional study of 70 patients with serologically confirmed syphilis at a Polish STI clinic. Oropharyngeal, anorectal, and urogenital samples were analysed by clustered logistic regression adjusted for site, stage, and log₂ Venereal Disease Research Laboratory (VDRL) titre.

Results

Among 171 samples, oropharyngeal positivity was highest (27/65, 41.5%). The adjusted model included 168 samples from 69 patients. Compared with urogenital sampling, oropharyngeal sampling had higher odds of positivity (adjusted odds ratio [aOR], 3.37; 95% CI, 1.50-7.55; P = .003). Late/unknown-duration syphilis had lower odds (aOR, 0.10; 95% CI, 0.03-0.35; P < .001), whereas each twofold VDRL increase raised the odds (aOR, 1.38; 95% CI, 1.06-1.78; P = .015). Overall, 64.6% of positive samples lacked local symptoms and objective findings.

Conclusions

Oropharyngeal positivity was frequent, particularly in early syphilis and at clinically normal sites. Oropharyngeal sampling warrants prospective evaluation as an adjunct to serology when lesion material is unavailable. Findings do not support routine screening of asymptomatic contacts or high-risk populations, HIV-specific testing, or serology replacement.