Long-Term Serologic Outcomes Following Treatment of Syphilis in People With HIV: A Prospective Cohort Study.

Abstract

This study aimed to evaluate the factors associated with rate and time to serological response, serofast status, and seroreversion in people with HIV (PWH) with a first diagnosis of syphilis. The primary endpoint was serological response as determined by a 4-fold decline in rapid plasma regain (RPR) titer or seroreversion at 12 months. A secondary endpoint was cumulative serological response by 24 months of follow-up. Survival and multivariate analysis were used to compare different associated factors. 184 PWH had a first syphilis episode in 642 person-years of follow-up. After treatment, median time to serological response was 6.53 months (95% CI, 6.055-7.012). In the Cox model, only secondary syphilis (HR 3.091, 95%CI 1.330-11.440; p=0.013), and higher nadir CD4+ count (HR 1.002; 95%CI 1.001-1.004; p=0.043) were associated with a faster response. At 12 months, 155 PWH (84%, 95%CI, 78%-89%) achieved response, and a lower baseline RPR (RR 0.972; 95%CI 0.947-0.997; p=0.028) was associated with failure. After response, 79 (51%) with higher CD4+ count remained as serofast status, and 33 of them (46%) seroreverted during follow-up. Of the 29 PWH without response, 11 (38%) reached serological response in a longer follow-up (29.3 months, 95%CI, 23.03-35.7), and 2 out of 4 (14%) had confirmed neurosyphilis, whereas 14 (48%) had a reinfection. Thus, 89% of PWH had serological response by 24 months. The time to serological response, the rate of serofast, and the outcome are the result of the interaction of non-treponemal test titers, syphilis stage, and the patient's immune status.