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Research Summary

Screening Tool to Identify Candidates for Pre-exposure HIV Prophylaxis in Men Who Have Sex with Men Includes Amphetamine and Alkyl Nitrite Use

Due to evidence that daily pre-exposure prophylaxis (PrEP) reduces the risk of HIV acquisition in men who have sex with men (MSM), the Food and Drug Administration approved an oral tenofovir/emtricitabine drug combination for daily use to prevent sexually acquired HIV infection. Researchers used data from 2 prospective randomized intervention trials (VaxGen’s VAX004 clinical trial and the HIV Prevention Trials Network’s EXPLORE study) to create a 7-item screening tool to identify MSM at highest risk for incident HIV infection who, thus, would be good candidates for PrEP. Data from each study were re-analyzed using multivariable logistic regression to determine risk factors associated with incident HIV infection. Data from the VAX004 were used to develop the risk index, and data from the EXPLORE study were used to validate the analysis.

  • The screening tool (the HIV Incidence Risk Index for MSM [HIRI-MSM]) included 7 factors that contributed the following number of points:
    • age (up to 8 points)
    • number of partners in the prior 6 months (up to 7 points)
    • number of HIV-positive partners in the prior 6 months (up to 8 points)
    • 1 or more events of unprotected receptive anal intercourse (10 points)
    • 5 or more unprotected insertive anal intercourse events (6 points)
    • use of amphetamines (5 points)
    • use of alkyl nitrite (3 points)
  • In the validation analysis, a score of >10 points identified individuals at high risk for HIV seroconversion with a sensitivity of 81%, a specificity of 38%, a positive predictive value of 1.2%, and a negative predictive value of 99.5%.


This HIV seroconversion prediction tool has the potential to screen MSM at increased risk of incident HIV infection who should be considered for PrEP. The tool does not identify candidates most likely to adhere to PrEP, which is a crucial factor in its implementation. Future research should include further validation of the HIRI-MSM in a prospective clinical sample that is more representative of MSM in the US (the study population was 5.6% African American, whereas African American patients account for 37% of incident HIV infection). James Daley, MPH,* & Alexander Y. Walley, MD, MSc
*Contributing Editorial Intern, Clinical Addiction Research and Education (CARE) Unit, Boston University School of Medicine, Boston, MA.


Smith DK, Pals SL, Herbst JH, et al. Development of a clinical screening index predictive of incident HIV infection among men who have sex with men in the United States. J Acquir Immune Defic Syndr. 2012;60(4):421–427.