Utility of Treponemal Testing from Aqueous Fluid in the Diagnosis of Ocular Syphilis in Patients with HIV/AIDS

Abstract

Purpose: Ocular syphilis is re-emerging globally especially in patients with human immunodeficiency virus (HIV). Atypical manifestations of ocular syphilis and/or other associated opportunistic infections often lead to a diagnostic dilemma. We evaluated the utility of aqueous humor (AH) Treponema pallidum hemagglutination assay (TPHA) titers in the diagnosis of ocular syphilis.

Methods: Retrospective case series of five HIV positive patients with positive syphilis serology in whom AH sampling was performed. All patients had ocular manifestations suspicious of infectious etiology.

Results: Panuveitis with/without retinitis was the commonest presentation. Along with blood investigations, polymerase chain reaction (PCR) testing from AH was done for Mycobacterium tuberculosis (MTB), Herpes Simplex Virus (HSV), Varicella Zoster Virus (VZV), Cytomegalovirus (CMV), and Toxoplasma gondii. In addition, serum antibody titers for Toxoplasma, rapid plasma reagin (RPR) and TPHA tests for syphilis were done. In patients with raised serum RPR/TPHA, aqueous TPHA titers were also assessed. Mean serum RPR titer was ≥ 1:32 and TPHA titer was ≥1:1280. Aqueous humor titers of TPHA was high in all patients (range ≥ 1:320 to ≥1:5120). Aqueous PCR was negative for all other infectious etiologies in four patients. In one patient, PCR-CMV was also positive, suggestive of a dual infection. Post-treatment with highly active antiretroviral therapy (HAART) and appropriate anti-syphilitic regime, complete resolution of lesions with corresponding fall in the serum RPR/TPHA titers were noted in all patients.

Conclusions: Ocular syphilis with atypical presentations is usually diagnosed based on a positive syphilis serology and by excluding other infectious causes. In the present study, we have shown an excellent correlation between raised AH TPHA titers with serological values and the clinical presentation. Considering the ease of collection of AH in contrast to vitreous fluids, the AH-TPHA assay could potentially be a valuable tool in the diagnosis of ocular syphilis.

Keywords: HIV/AIDS; Ocular syphilis; aqueous humor; aqueous humor TPHA titers; polymerase chain reaction; serum treponema pallidum hemagglutination.