Open Access Open Badges 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

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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.