Ocular syphilis in patients with nonreactive RPR and positive treponemal serologies: a retrospective observational cohort study.

Background: Screening for syphilis increasingly relies on positive treponemal rather than nontreponemal tests (rapid plasma reagin [RPR]). We compared ocular syphilis in patients with nonreactive versus positive RPR.
Methods: We conducted a retrospective observational cohort study of ocular syphilis treated at two New England hospitals 1996-2021 based on ophthalmologist-diagnosed eye findings and positive treponemal serology, regardless of RPR. We excluded patients with alternative diagnoses. We categorized RPR into nonreactive RPR, low-titer RPR (<1:8), and high-titer RPR (≥1:8) and compared early and long-term response to therapy.
Results: Our sample included 115 patients with ocular syphilis (median follow-up 2.5 years): 25 (22%) nonreactive RPR, 21 (18%) low-titer RPR, 69 (60%) high-titer RPR. Compared with nonreactive and low-titer RPR, people with high-titer RPR were younger (mean 47 years, p<0.001), more likely male (93%, p<0.001) and more likely to be living with HIV (49%, p<0.001). People with nonreactive and low-titer RPR were less likely than high-titer RPR to have posterior/panuveitis (32% and 29% versus 75%, p<0.001) or abnormal CSF (26% and 35% versus 75%, p<0.001), and more likely to present with chronic eye findings (20% and 29% versus 1%, p<0.001). In long-term follow up, eye findings improved and did not recur in most patients (62% nonreactive, 68% low-titer, 96% high-titer RPR); improved but recurred in 29%, 11%, and 4%, respectively; and were stable in 10%, 21%, and 0%, respectively.
Conclusion: Patients with ocular syphilis and nonreactive RPR are similar to patients with low-titer RPR, and antibiotic therapy is beneficial in most.
(© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)