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 polymerase chain reaction positivity across anatomical sites and assess whether oropharyngeal sampling warrants prospective evaluation as an adjunct to serology in suspected early syphilis when suitable lesion material is unavailable.

METHODS

We conducted a retrospective cross-sectional study of 70 patients with serologically confirmed syphilis at a Polish sexually transmitted infection clinic. Oropharyngeal, anorectal, and urogenital samples were analyzed using clustered logistic regression adjusted for site, stage, and log₂ Venereal Disease Research Laboratory (VDRL) titer.

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 = 0.003). Late or unknown-duration syphilis had lower odds (aOR, 0.10; 95% CI, 0.03-0.35; P < 0.001), whereas each 2-fold VDRL increase raised the odds (aOR, 1.38; 95% CI, 1.06-1.78; P = 0.015). Overall, 64.6% of positive samples lacked local symptoms and objective findings.

CONCLUSION

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. These findings do not support routine screening of asymptomatic contacts or high-risk populations, HIV-specific testing, or replacement of serology.