BackgroundPersons seeking emergency injury care are often from underserved key populations (KPs) and priority populations (PPs) for HIV programming. While facility-based HIV Testing Services (HTS) in Kenya are effective, emergency department (ED) delivery is limited, despite the potential to reach underserved persons.MethodsThis quasi-experimental prospective study evaluated implementation of the HIV Enhanced Access Testing in Emergency Departments (HEATED) at Kenyatta National Hospital ED in Nairobi, Kenya. The HEATED program was designed using setting specific data and utilizes resource reorganization, services integration and HIV sensitization to promote ED-HTS. KPs included sex workers, gay men, men who have sex with men, transgender persons and persons who inject drugs. PPs included young persons (18-24 years), victims of interpersonal violence, persons with hazardous alcohol use and those never previously HIV tested. Data were obtained from systems-level records, enrolled injured patient participants and healthcare providers. Systems and patient-level data were collected during a pre-implementation period (6 March - 16 April 2023) and post-implementation (period 1, 1 May - 26 June 2023). Additional, systems-level data were collected during a second post-implementation (period 2, 27 June – 20 August 2023). Evaluation analyses were completed across reach, effectiveness, adoption, implementation and maintenance framework domains.ResultsAll 151 clinical staff were reached through trainings and sensitizations on the HEATED program. Systems-level ED-HTS increased from 16.7% pre-implementation to 23.0% post-implementation periods 1 and 2 (RR=1.31, 95% CI:1.21-1.43; p<0.001) with a 62.9% relative increase in HIV self-test kit provision. Among 605 patient participants, facilities-based HTS increased from 5.7% pre-implementation to 62.3% post-implementation period 1 (RR=11.2, 95%CI:6.9-18.1; p<0.001). There were 440 (72.7%) patient participants identified as KPs (5.6%) and/or PPs (65.3%). For enrolled KPs/PPs, HTS increased from 4.6% pre-implementation to 72.3% post-implementation period 1 (RR=13.8, 95%CI:5.5-28.7, p<0.001). Systems and participant level data demonstrated successful adoption and implementation of the HEATED program. Through 16-weeks post-implementation a significant increase in ED-HTS delivery was maintained as compared to pre-implementation.ConclusionsThe HEATED program increased ED-HTS and augmented delivery to KPs/PPs, suggesting that broader implementation could improve HIV services for underserved persons, already in contact with health systems.