PROJECT SUMMARY / ABSTRACT Roughly 1 in 8 Americans living with HIV are unaware of their infection. As an entry point into the healthcare system, emergency departments (EDs) are uniquely positioned to help reduce this burden of undiagnosed HIV in the U.S. A growing amount of all healthcare in the U.S. is delivered in an ED setting. Unfortunately, compared with other settings, EDs have some of the lowest HIV testing rates. These rates further declined leading up to the COVID-19 pandemic and despite renewed efforts in the Ending the HIV Epidemic in the U.S. (EHE) initiative. Decreasing testing rates appear to stem from several barriers, including concerns about cost and the impact of increased testing on overcrowding and boarding. Unfortunately, few studies have focused on exploring these barriers, either since EHE’s launch or following the COVID-19 pandemic. The primary purpose of this award is to provide Dr. Christopher Bennett, Assistant Professor of Emergency Medicine at Stanford University, the support necessary to facilitate their long-term goals to (1) help EDs lead the charge in ending the HIV epidemic in the U.S. and (2) transition from a junior investigator to an independent physician–scientist with expertise in economic analyses, implementation science, and qualitative methods. In Aim 1, Dr. Bennett will train in economic analyses to investigate the cost-effectiveness of ED-based HIV screening in geographic areas targeted by EHE compared against current screening rates and then determine the incremental cost-effectiveness of HIV screening in all U.S. EDs. In Aims 2 and 3, the candidate will innovatively leverage a recent California initiative in which 28 local EDs received funding to implement or expand routine, opt-out HIV screening. Specifically, in Aim 2, Dr. Bennett will train in implementation science to create a typology of the screening strategies used by these EDs; this work will be informed by a stakeholder group of ED leaders with efforts guided by the Reach, Effectiveness, Adoption, Implementation, Maintenance (RE-AIM) framework. In Aim 3, Dr. Bennett will obtain additional training in qualitative methods to employ semi-structured interviews of a diverse cohort – frontline ED providers implementing HIV screening and persons tested for HIV at these EDs – at a subset of these sites to illuminate firsthand barriers and facilitators encountered during the real-world implementation of HIV screening programs, guided by the updated Consolidated Framework for Implementation Research (CFIR). This K08 award is designed to leverage Dr. Bennett’s clinical training and build upon their background in epidemiology and health services research. This innovative K08 responds to several NIH priorities for HIV and HIV-related research and will aid decision makers in identifying which strategies work for different communities. Overall, this work will advance EHE’s mission to make HIV screening routine in all settings that serve a high volume of ra...