UCLA UCLA Electronic Theses and Dissertations Title Formulation of a Novel HIV-Risk Algorithm for Men who have Sex with Men Visiting a Community-Based Clinic in Los Angeles, California Permalink https://escholarship.org/uc/item/6br376xv Author Beymer, Matthew R. Publication Date 2015 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA Los Angeles Formulation of a Novel HIV-Risk Algorithm for Men who have Sex with Men Visiting a Community-Based Clinic in Los Angeles, California A dissertation submitted in satisfaction of the requirements for the degree of Doctor of Philosophy in Public Health by Matthew Beymer 2015 © Copyright by Matthew Beymer 2015 ABSTRACT OF THE DISSERTATION Formulation of a Novel HIV-Risk Algorithm for Men who have Sex with Men Visiting a Community-Based Clinic in Los Angeles, California by Matthew Beymer Doctor of Philosophy in Public Health University of California, Los Angeles, 2015 Professor Linda B. Bourque, Chair Statement of the Problem: Men who have sex with men (MSM) make up only 2% of the population in the United States, but represent 60% of all HIV infections each year. Pre-exposure prophylaxis (PrEP), a once daily medication to prevent HIV infection, has emerged as a prevention tool for populations most heavily affected by HIV. However, the criteria for PrEP have only been broadly defined and lead many individuals and their medical providers to question if PrEP use is appropriate, given individual risk profile and potential drug side effects. The primary goal of this dissertation is to use risk assessment and HIV testing data to create an HIV risk score for HIV-negative MSM. The secondary goal is to use this HIV risk score to create more targeted criteria for PrEP use and subsequently inform individualized PrEP candidacy. Methods: Behavioral risk assessment and HIV testing data were collected at the Los Angeles ii LGBT Center from January 2009 to June 2014. Individuals were included in the analysis if they were MSM, had an HIV-negative test result at baseline, and returned for at least one follow-up HIV testing visit (n = 9,981). Bivariate and Multivariate Cox Proportional Hazards Models were used to determine the biological, behavioral, and substance use variables significant in HIV contraction over the 5.5 year follow-up period. Summary of Findings: Self-reported history of gonorrhea (p = 0.03), chlamydia (p < 0.0001), and syphilis (p = 0.01); having receptive anal sex (p < 0.0001), race/ethnicity of partners (p = 0.005), and number of sexual partners in the last three months (p = 0.0003); methamphetamine (p = 0.0008), and nitrate use (p = 0.002) were all significant predictors of HIV infection during follow-up. Age of partners, intimate partner violence, and ecstasy use were not significant. Following risk score creation, approximately 45% of all individuals were above a chosen risk score, which consisted of 76% of all HIV-positives. The use of this targeted strategy is beneficial in that it more accurately outlines PrEP candidacy criteria, subsequently allowing individuals and their medical providers to make a more informed decision before use. iii The dissertation of Matthew Beymer is approved. Gilbert C. Gee Donald E. Morisky Suzanne B. Shu Robert E. Weiss Linda B. Bourque, Committee Chair University of California, Los Angeles 2015 iv To Bob, Catherine and the Committee, the physician with the brilliant idea, the statistician who showed patience and kindness to a fledgling scientist, and the group who committed to completing the dream v TABLE OF CONTENTS LIST OF FIGURES ..................................................................................................................... ix LIST OF TABLES ....................................................................................................................... xi LIST OF EQUATIONS ............................................................................................................. xiv LIST OF ACRONYMS ............................................................................................................. xiv SIGNIFICANCE TESTING AND DATA PRESENTATION ................................................ xv GLOSSARY................................................................................................................................. xv ACKNOWLEDGEMENTS .................................................................................................... xviii VITA/BIOGRAPHICAL SKETCH ......................................................................................... xix Chapter 1 – Introduction ............................................................................................................. 1 HIV Incidence in the United States ............................................................................................. 1 Biomedical Tools to Prevent HIV Infection ............................................................................... 2 Formulation of an HIV Risk Algorithm for HIV-Negatives ....................................................... 5 Chapter 2 – Study Objective, Specific Aims, and Research Questions.................................... 9 Aim 1 – Calculate HIV Risk Score ........................................................................................... 11 Aim 2 – Use the HIV Risk Score to Inform Intervention Strategy ........................................... 12 Aim 3 – Assess Circumstances for HIV Infection among At-Risk Subgroups ........................ 14 Chapter 3 – Theoretical Background ........................................................................................ 16 Information-Motivation-Behavioral Skills Model .................................................................... 16 Syndemics Theory ..................................................................................................................... 21 Limitations to Presented Theories ............................................................................................. 30 Chapter 4 – Background and Literature Review..................................................................... 32 Biological Variables .................................................................................................................. 32 Sexual Behavioral Variables ..................................................................................................... 36 Substance Use Variables ........................................................................................................... 40 Control Variables ...................................................................................................................... 42 Limitations to the Literature Findings ....................................................................................... 45 Summary of Literature Findings ............................................................................................... 47 Chapter 5 – Research Design and Methods .............................................................................. 49 Study Population ....................................................................................................................... 49 vi Dependent Variable ................................................................................................................... 50 Independent Variables ............................................................................................................... 51 Control Variables ...................................................................................................................... 58 Summary of Variable Relationships ......................................................................................... 59 Analytical Procedures ............................................................................................................... 60 Imputation of STI and HIV Data............................................................................................... 63 Chapter 6 – Bivariate Results .................................................................................................... 67 Bivariate Survival Analyses – Biological Predictors ................................................................ 67 Bivariate Survival Analyses – Sexual Behavioral Predictors ................................................... 76 Bivariate Survival Analyses – Substance Use Predictors ......................................................... 84 Bivariate Survival Analyses – Demographic Predictors ........................................................... 89 Investigating Interactions and Different Circumstances for HIV ............................................. 93 Bivariate Survival Analyses for African-American and Hispanic MSM Subgroups.............. 100 Bivariate Survival Analyses for Young MSM Subgroup........................................................ 111 Chapter 7 – Multivariate Results ............................................................................................ 121 Variable Selection for the Multivariate Models ...................................................................... 121 Multivariate Results among the Entire Population ................................................................. 124 Construction of the HIV Risk Algorithm ................................................................................ 126 Multivariate Results among At-Risk Subgroups ....................................................................