Predictive Factors for HIV Seroconversion Among Individuals Attending a Specialized Center After an HIV Risk Exposure: A Case-Control Study

Objective: To better target our current prevention strategies, we assessed factors associated with HIV seroconversion in individuals attending a specialized center after a risk exposure. Materials and Methods: We studied individuals from an HIV Unit's contact risk cohort at a tertiary care hospital in Barcelona, Spain, between 2003 and 2013 and performed a retrospective matched case-control study. Cases were individuals who seroconverted to HIV after at least 3 months since first follow-up visit for a contracting risk. Controls were HIV-negative individuals from the same cohort. Demographics and behavior variables were studied and compared using a McNemar test assessing factors associated with seroconversion. Univariate analysis and binary logistic regression were performed to develop a model for predicting probability of HIV seroconversion. We also evaluated sensitivity and specificity of our model and an area under Receiver Operating Characteristic (ROC) curve was estimated. Results: Sixty-nine (2.2%) individuals seroconverted after a median (interquartile range) of 24 (9-34) months since last follow-up. Seroconverters were predominantly male (96%) and men who have sex with men (MSM) (94%). No differences were observed regarding risk of exposure. Being MSM [odds ratio (OR) 5.2 (1.4-20.2), p=.01], having a known HIV-positive partner [OR 2.7 (1.2-6.2), p=.02], previous postexposure prophylaxis (PEP) [OR 3.9 (1.0-15.6), p=.05], and having previous sexually transmitted infections (STIs) [OR 4.6 (1.9-10.9), p=.001] were the factors independently associated with HIV seroconversion. The sensitivity and specificity of our model were 64.06% and 73.53%, respectively, and the area under ROC curve was 0.777. Discussion: HIV seroconversions were observed frequently between individuals attending a specialized center because of a risk exposure. Being MSM, having had previous PEP, an HIV-positive sexual partner, and previous STI were predictive factors for HIV seroconversion. Closer and longer follow-up and/or pre-exposure prophylaxis should be considered to prevent HIV infections in this high-risk population.