Clarifying the volume of estimated need for public health and prevention services within an emergency department population

OBJECTIVES: Emergency departments (EDs) are called to implement public health and prevention initiatives, such as infectious disease screening. The perception that ED resources are insufficient is a primary barrier. Resource needs are generally conceptualized in terms of total number of ED encounters, without formal calculation of the number of encounters for which a service is required. We illustrate potential differences in the estimated volume of service need relative to ED census using the examples of HIV and hepatitis C (HCV) screening. METHODS: This cross‐sectional analysis adjusted the proportion of ED encounters in which patients are eligible for HIV and HCV screening according to a cascade of successively more restrictive patient selection criteria, presuming full implementation of each criterion. Parameter estimates for the proportion satisfying each selection criterion were derived from the electronic health records of an urban academic facility and its ED HIV and HCV screening program during 2 time periods. The primary outcome was the estimated reduction in proportion of ED visits eligible for screening after application of the entire cascade. RESULTS: There were 76,104 ED encounters during the study period. Applying all selection criteria reduced the number of required screens by 97.1% (95% confidence interval, 97.0–97.2) for HIV and 86.1% (95% confidence interval, 85.9–86.3) for HCV. CONCLUSIONS: Using the example of HIV and HCV screening, the application of eligibility metrics reduces the volume of service need to a smaller, more feasible number than estimates from ED census alone. This approach might be useful for clarifying perceived service need and guiding operational planning.