Rapid Plasma Reagin Tests of Serum, Cerebrospinal Fluid, and Aqueous Humor of Patients With Ocular Syphilis and AIDS

Purpose The diagnosis of ocular syphilis in patients with acquired immunodeficiency syndrome (AIDS) remains challenging. This study aimed to evaluate the potential utility of aqueous humor (AH) RPR testing as an adjunctive diagnostic tool for assessing clinical manifestations and visual function in AIDS‐associated ocular syphilis. Methods We conducted a retrospective observational cohort study of 31 patients (42 eyes) with ocular syphilis and AIDS treated at Beijing You’an Hospital between 2022 and 2025, based on comprehensive ophthalmic and systemic evaluations. Results In patients with concurrent syphilis and AIDS, a higher pretreatment AH RPR reactivity level was associated with higher vitreous haze grades (OR = 4.10, 95% CI: 1.62–10.38, p = 0.003). Pretreatment serum, CSF, and AH RPR titers individually predicted macular chorioretinal involvement (AUC 0.76–0.85) and optic nerve involvement (AUC 0.62–0.78). Combining all three markers improved prediction for macular chorioretinal involvement (AUC 0.88) and for optic nerve involvement (AUC 0.79). RPR titers in serum, CSF, and AH were all significantly correlated with both pre‐ and posttreatment best‐corrected visual acuity, indicating that higher titers were associated with worse visual function. Conclusion AH RPR can serve as a valuable adjunct for diagnosing ocular syphilis, as it indicates intraocular disease activity and informs treatment recommendations for the condition. Trial Registration: Chinese Clinical Trial Registry: 2200056954