Background: HIV-1 risk scoring tools could help target provision of prevention modalities such as pre-exposure prophylaxis (PrEP). Recent research suggests that risk scores for women aged 18-45 may not predict risk well among young women aged 18-24. We evaluated the predictive performance of age-specific risk scores compared to the existing non-age-specific VOICE risk score, developed for women aged 18-45.

Methods: We conducted a secondary analysis of the Evidence for Contraceptive Options and HIV Outcomes Trial to develop and internally validate HIV-1 risk scores for women aged 18-24 and 25-35 in South Africa. Candidate predictors included baseline demographic, clinical, behavioral, and contextual characteristics readily available in clinical settings. The VOICE risk score was applied to women aged 18-35. We evaluated predictive performance of each risk score by area under the receiver operating characteristic curve (AUC).

Results: Predictive performance of all risk scores was moderate, with AUC (95% CI) of 0.64 (0.60, 0.67) among women aged 18-24, 0.68 (0.62, 0.73) among those aged 25-35, and 0.61 (0.58 0.65) for the VOICE risk score applied to women aged 18-35; AUC was similar in internal validation. Among women aged 18-24, HIV-1 incidence was high even at low risk scores, at 3.9 per 100 person-years (95% CI: 3.2, 4.7).

Conclusion: All risk scores were moderately predictive of HIV-1 acquisition, and age-specific risk scores performed only marginally better than the VOICE non-age-specific risk score. Approaches for targeted PrEP provision to women in South Africa may require more extensive data than are currently available to improve prediction.