Estimating Mediation and Moderation Effects in HIV Care Continuum Intervention Trials for People who Use Drugs

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PROJECT SUMMARY The overall goal of this study is to conduct secondary analyses of available randomized controlled trial (RCT) intervention data to gain actionable knowledge about how to improve HIV care continuum (HIV-CC) outcomes among people living with HIV who use drugs (PLWHUD). Specifically, we will use available data from four different RCTs to their full potential by analyzing mediators and moderators of efficacy that were not tested during the original outcome analysis of the respective trials. The RCTs tested different HIV-CC interventions for PLWHUD: 1) ARCS, which tested a community and individual level stigma reduction intervention for people living with HIV who inject drugs in Vietnam; 2) HOPE, which tested patient navigation and contingency management among hospital patients in the U.S. living with HIV with co-occurring substance use disorder; 3) LINC, which tested a strengths-based patient navigation intervention among hospital patients in Russia living with HIV with co-occurring injection drug use; and 4) HPTN 074, a HIV Prevention Trials Network RCT that tested an intervention involving systems navigation, psychosocial counseling, and ART initiation among people living with HIV who inject drugs in Vietnam, Indonesia, and Ukraine. Specific aims include: 1) Determine how and for whom HIV-CC interventions improve biological outcomes (viral suppression, CD4, mortality) among PLWHUD. For this aim we will test concordant hypotheses across all four trials about theory-based mediators and substance use mediators, as well as moderators, and conditional process models (that simultaneously test mediators and moderators in a single model); 2) Examine which specific mediators primarily affect HIV-CC outcomes among subgroups of PLWHUD using newer causal mediation analysis to strengthen causal inference; and 3) We will review our evidence to date to disseminate how HIV behavioral interventionists can meet improved standards for complete evaluations in RCTs (i.e., test mediators plus moderators). The research is led by experts in HIV prevention and care among vulnerable populations, including people who use drugs, and experts in advanced mediation and moderation analysis. The study activities and deliverables will also be informed by a Scientific Advisory Committee comprised of the original Principal Investigators from each of the four trials, as well as an original Co-Investigator from each of the trials. These individuals include some of the leading experts in HIV-CC engagement for people who use drugs and will be instrumental to informing the analyses and interpretation of results. The research builds on our previous NIH R01-funded research that demonstrated how mediation and moderation analyses help to shed new light on efficacious and non-efficacious results found in HIV prevention RCTs. Moving beyond our previous research, in the current study we will disseminate accessible tools to the HIV field that should improve our evaluation of interventions, and that will accelerate the impact of each future RCT. Last, by analyzing drug use-related variables we gain valuable insight into the role of drug use in the efficacy of HIV-CC interventions for PLWHUD, a critical population to support in order to end the HIV epidemic.