An Empiric Risk Scoring Tool for Identifying High-Risk Heterosexual HIV-1–Serodiscordant Couples for Targeted HIV-1 Prevention

BACKGROUND AND OBJECTIVES: Heterosexual HIV-1-serodiscordant couples are increasingly recognized as an important source of new HIV-1 infections in sub-Saharan Africa. A simple risk assessment tool could be useful for identifying couples at highest risk for HIV-1 transmission. METHODS: Using data from 3 prospective studies of HIV-1-serodiscordant couples from 7 African countries and standard methods for development of clinical prediction rules, the authors derived and validated a risk scoring tool developed from multivariate modeling and composed of key predictors for HIV-1 risk that could be measured in standard research and clinical settings. RESULTS: The final risk score included age of the HIV-1-uninfected partner, married and/or cohabiting partnership, number of children, unprotected sex, uncircumcised male HIV-1-uninfected partner, and plasma HIV-1 RNA in the HIV-1-infected partner. The maximum risk score was 12, scores ≥5 were associated with an annual HIV-1 incidence of >3%, and couples with a score ≥6 accounted for only 28% of the population but 67% of HIV-1 transmissions. The area under the curve for predictive ability of the score was 0.74 (95% confidence interval: 0.70 to 0.78). Internal and external validation showed similar predictive ability of the risk score, even when plasma viral load was excluded from the risk score. CONCLUSIONS: A discrete combination of clinical and behavioral characteristics defines highest risk HIV-1-serodiscordant couples. Discriminating highest risk couples for HIV-1 prevention programs and clinical trials using a validated risk score could improve research efficiency and maximize the impact of prevention strategies for reducing HIV-1 transmission.