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

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.

A total of 184 PWH had a first syphilis episode in 642 person-years of follow-up. After treatment, the 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 = .013) and higher nadir CD4+ count (HR 1.002; 95% CI 1.001-1.004; P = .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 .947-.997; P = .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 reinfections. 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 nontreponemal test titers, syphilis stage, and the patient's immune status.