Objectives: The ''emergency department algorithm'' (EDA) uses emergency department (ED) diagnoses to assign probabilities that a visit falls into each of four categories: nonemergency, primary care-treatable emergency, preventable emergency needing ED care, and nonpreventable emergency. The EDA's developers report that it can evaluate the medical safety net because patients with worse access to care will use EDs for less urgent conditions. After the Oregon Health Plan (OHP, Oregon's expanded Medicaid program) underwent cutbacks affecting access to care in 2003, the authors tested the ability of the EDA to detect changes in ED use.Methods: All visits to 22 Oregon EDs during 2002 were compared with visits during 2004. For each payer category, mean probabilities that ED visits fell into each of the four categories were compared before versus after the OHP cutbacks.Results: The largest change in mean probabilities after the cutbacks was 2%. Attempts to enhance the sensitivity of the EDA through other analytic strategies were unsuccessful. By contrast, ED visits by the uninsured increased from 6,682 ⁄ month in 2002 to 9,058 ⁄ month in 2004, and the proportion of uninsured visits leading to hospital admission increased by 51%.
Conclusions:The EDA was less useful in demonstrating changes in access to care than were other, simpler measures. Methodologic concerns with the EDA that may account for this limitation are discussed. Given the widespread adoption of the EDA among health policy researchers, the authors conclude that further refinement of the methodology is needed.
ACADEMIC EMERGENCY MEDICINE 2008; 15:506-516 ª 2008 by the Society for Academic Emergency MedicineKeywords: access to care, emergency department, Medicaid, measurement, methodology T he concept of ambulatory care-sensitive hospitalizations 1,2 led to a valuable tool for monitoring access to primary care. This methodology was developed by Billings and colleagues, 1,2 who demonstrated that hospitalization rates for conditions such as asthma, diabetes mellitus, and hypertension were strongly associated with poor access. Their work has been replicated and expanded by others.3-10 Ambulatory care-sensitive hospitalization rates have become a widely recognized tool for assessing access to care; this approach has been incorporated into a toolkit developed by the Agency for Healthcare Research and Quality (AHRQ) for monitoring the safety net.
11,12This same toolkit includes a methodology developed by Billings and colleagues for studying emergency department (ED) visits as a measure of access to care. 13-15 ED utilization rates vary by insurance status, socioeconomic status, race, and other economic and social factors, [16][17][18][19][20][21][22][23][24][25] confirming the clinical experience of many emergency physicians (EPs)-that patients often use the ED as a safety net for lack of access to care elsewhere. A common perception is that patients with poor access to care often use the ED for ''nonurgent'' or ''inappropriate'' problems that could be trea...