Hospital-free days: A novel measure to study outcomes for emergency department care

Traditionally, researchers have evaluated the quality of emergency care using subsequent adverse events, like mortality or return hospital visits. The selection of these well-defined, single events as outcomes for epidemiological studies has strengths, including ease of interpretation. Yet any particular outcome only captures part of the story of how patients fare after receiving care in the emergency department (ED).

For example, mortality is a clinically significant outcome. It fails, however, to capture quality of life decrements that may be important to patients and families. Furthermore, its rarity necessitates prohibitively large sample sizes. By contrast, composite outcome measures such as major adverse cardiac events require less statistical power but assume that all component parts (e.g., death and hospitalization) are valued equally by patients.

Hospital-free days (HFD) offer a potential solution, naturally combining morbidity and mortality to create an easily calculated, patient-centered measure sensitive to high-quality emergency care. Essentially synonymous with days alive and out of hospital (DAOH), and similar in concept to other metrics including healthy days at home (HDAH), HFD is gaining acceptance in health services, epidemiological, and comparative effectiveness research. However, these metrics have only recently been used in emergency medicine research. In this commentary, we outline the HFD approach, discuss unique considerations to using HFD to study emergency medicine outcomes, and propose development of standardized approaches for emergency medicine research.

Ari B Friedman, M Kit Delgado, Catherine L Auriemma, Austin S Kilaru