Development and validation of the San Diego Early Test Score to predict acute and early HIV infection risk in men who have sex with men

Abstract

Background: Although men who have sex with men (MSM) represent a dominant risk group for human immunodeficiency virus (HIV), the risk of HIV infection within this population is not uniform. The objective of this study was to develop and validate a score to estimate incident HIV infection risk.

Methods: Adult MSM who were tested for acute and early HIV (AEH) between 2008 and 2014 were retrospectively randomized 2:1 to a derivation and validation dataset, respectively. Using the derivation dataset, each predictor associated with an AEH outcome in the multivariate prediction model was assigned a point value that corresponded to its odds ratio. The score was validated on the validation dataset using C-statistics.

Results: Data collected at a single HIV testing encounter from 8326 unique MSM were analyzed, including 200 with AEH (2.4%). Four risk behavior variables were significantly associated with an AEH diagnosis (ie, incident infection) in multivariable analysis and were used to derive the San Diego Early Test (SDET) score: condomless receptive anal intercourse (CRAI) with an HIV-positive MSM (3 points), the combination of CRAI plus ≥5 male partners (3 points), ≥10 male partners (2 points), and diagnosis of bacterial sexually transmitted infection (2 points)-all as reported for the prior 12 months. The C-statistic for this risk score was >0.7 in both data sets.

Conclusions: The SDET risk score may help to prioritize resources and target interventions, such as preexposure prophylaxis, to MSM at greatest risk of acquiring HIV infection. The SDET risk score is deployed as a freely available tool at http://sdet.ucsd.edu.

Keywords: MSM; acute and early HIV; risk behavior; risk score.

Figure 1.

Distribution of San Diego Early Test (SDET) score in the validation cohort in human immunodeficiency virus (HIV)–uninfected individuals (white bars) and those with acute and early HIV (AEH) infection (black bars).

Figure 2.

The San Diego Early Test (SDET) score online tool with intuitive sliders (track bars) that allow users to easily select relevant risk behaviors across the 4 dimensions central to the SDET score. After answering some basic demographic questions (used to anonymously map reported risk behavior to population-level data), users will select their risk behaviors. Once this is set, they will receive immediate feedback in terms of their current human immunodeficiency virus (HIV) risk, as indicated by the colored bars on the “risk meter.” After users receive their risk score, the online SDET tool invites them to explore how their risk changes when they change behavior. By moving the scroll bars, users see the direct impact of behavior change on their HIV risk score. If users agree, the tool automatically sends each user a reminder to participate again 12 months later, which will allow exploration of linkage between increased risk awareness and effective behavior change. Available at http://sdet.ucsd.edu.