Objectives: To examine how emergency department (ED) overcrowding has been defined in the medical literature.
Methods: Using the National Library of Medicine's PubMed and MEDLINE databases (1966 to 2002), a comprehensive review of the English-language medical literature was conducted to identify explicit criteria for defining ED overcrowding. Inclusion criteria were original articles, editorials, and reviews; news articles and letters to the editor were excluded. Using a standardized extraction form, publications were described as primary if the title or an objective statement in the introductory or methods paragraph referred to crowding or overcrowding; all other citations were categorized as secondary. Each report was then evaluated to determine whether crowding or overcrowding was defined explicitly or implicitly. Explicit definitions included phrases such as "Crowding was defined as ..." or "Overcrowding occurred when ..."; other definitions were characterized as implicit.
Results: A total of 231 candidate articles were identified; 91 met inclusion criteria, and 53 (58%) were primary articles about ED crowding or overcrowding. Among these primary articles, 23 (43%) had explicit definitions of crowding or overcrowding. The definitions varied widely in content and focus, including ED, hospital, or external (nonhospital) factors.
Conclusions: Although ED overcrowding has been a topic of frequent investigation, current definitions of the problem are often implicit or focus on factors outside of the ED itself. A more consistent approach to defining ED overcrowding would help to clarify the distinctions between causes, characteristics, and outcomes of overcrowding.