Evaluating the Screening and Enrollment of People at Risk of HIV in Mexico’s Preexposure Prophylaxis Demonstration Project, 2018-2020

Objectives: Screening tools in which participants self-report sexual behaviors can identify people at risk of HIV acquisition for enrollment in preexposure prophylaxis (PrEP). We compared enrollment outcomes (ie, receiving PrEP vs being excluded by a counselor or declining PrEP) in Mexico’s PrEP demonstration project and evaluated the validity of a 4-criteria PrEP eligibility tool in which participants self-reported risk behavior—having condomless anal sex, transactional sex, a partner living with HIV, or a sexually transmitted infection—as compared with PrEP eligibility assessed by a counselor. Methods: We recruited men who have sex with men and transwomen who were offered PrEP services in Mexico. We characterized participants according to enrollment outcome and identified underlying factors through logistic regression analyses. We calculated the sensitivity and specificity of the self-reported risk criteria, using the counselor’s risk assessment as the point of reference. Results: Of 2460 participants, 2323 (94%) had risk criteria of HIV acquisition according to the 4-criteria tool; 1701 (73%) received PrEP, 247 (11%) were excluded by a counselor, and 351 (15%) declined PrEP despite being considered eligible by the counselor. Participants who were excluded or who declined PrEP were less likely to report HIV risk behaviors than those who received PrEP, and participants who declined PrEP were more likely to be transwomen (vs men who have sex with men) and aged ≤25 years (vs >25 y). The 4-criteria risk tool had high sensitivity (98.6%) and low specificity (29.8%). Conclusion: The screening tool identified most participants at risk of HIV acquisition, but counselors’ assessment helped refine the decision for enrollment in PrEP by excluding those with low risk. Public health strategies are needed to enhance enrollment in PrEP among some groups.