Email updates

Keep up to date with the latest news and content from BMC Health Services Research and BioMed Central.

Open Access Research article

Defining emergency department episodes by severity and intensity: A 15-year study of Medicare beneficiaries

Brian Kaskie1*, Maksym Obrizan2, Elizabeth A Cook3, Michael P Jones45, Li Liu5, Suzanne Bentler1, Robert B Wallace38, John F Geweke6, Kara B Wright3, Elizabeth A Chrischilles3, Claire E Pavlik7, Robert L Ohsfeldt8, Gary E Rosenthal149 and Fredric D Wolinsky,19

Author Affiliations

1 Department of Health Management and Policy, College of Public Health, the University of Iowa, Iowa City, Iowa, USA

2 Kyiv School of Economics, and Kyiv Economics Institute, Kyiv, Ukraine

3 Department of Epidemiology, College of Public Health, the University of Iowa, Iowa City, Iowa, USA

4 Center for Research on the Implementation of Innovative Strategies into Practice, Iowa City Veterans Administration Medical Center, Iowa City, Iowa, USA

5 Department of Biostatistics, College of Public Health, the University of Iowa, Iowa City, Iowa, USA

6 Department of Economics, Tippie College of Business, the University of Iowa, Iowa City, Iowa, USA

7 Department of Geography, College of Liberal Arts and Sciences, the University of Iowa, Iowa City, Iowa, USA

8 Department of Health Management and Policy, School of Rural Public Health, Texas A&M University Health Science Center, College Station, Texas, USA

9 Department of Internal Medicine, Carver College of Medicine, the University of Iowa, Iowa City, Iowa, USA

For all author emails, please log on.

BMC Health Services Research 2010, 10:173  doi:10.1186/1472-6963-10-173

Published: 21 June 2010



Episodes of Emergency Department (ED) service use among older adults previously have not been constructed, or evaluated as multi-dimensional phenomena. In this study, we constructed episodes of ED service use among a cohort of older adults over a 15-year observation period, measured the episodes by severity and intensity, and compared these measures in predicting subsequent hospitalization.


We conducted a secondary analysis of the prospective cohort study entitled the Survey on Assets and Health Dynamics among the Oldest Old (AHEAD). Baseline (1993) data on 5,511 self-respondents ≥70 years old were linked to their Medicare claims for 1991-2005. Claims then were organized into episodes of ED care according to Medicare guidelines. The severity of ED episodes was measured with a modified-NYU algorithm using ICD9-CM diagnoses, and the intensity of the episodes was measured using CPT codes. Measures were evaluated against subsequent hospitalization to estimate comparative predictive validity.


Over 15 years, three-fourths (4,171) of the 5,511 AHEAD participants had at least 1 ED episode, with a mean of 4.5 episodes. Cross-classification indicated the modified-NYU severity measure and the CPT-based intensity measure captured different aspects of ED episodes (kappa = 0.18). While both measures were significant independent predictors of hospital admission from ED episodes, the CPT measure had substantially higher predictive validity than the modified-NYU measure (AORs 5.70 vs. 3.31; p < .001).


We demonstrated an innovative approach for how claims data can be used to construct episodes of ED care among a sample of older adults. We also determined that the modified-NYU measure of severity and the CPT measure of intensity tap different aspects of ED episodes, and that both measures were predictive of subsequent hospitalization.