title: Impact of the Affordable Care Act Medicaid expansion on emergency department high utilizers with ambulatory care sensitive conditions: A cross-sectional study.
abstract: OBJECTIVE
  The effect of the Affordable Care Act on emergency department (ED) high utilizers has not yet been thoroughly studied. We sought to determine the impact of changes in insurance eligibility following the 2014 Medicaid expansion on ED utilization for ambulatory care sensitive conditions (ACSC) by high ED utilizers in an urban safety net hospital.
  
  
  METHODS
  High utilizers were defined as patients with ≥4 visits in the 6months before their most recent visit in the study period (July-December before and after Maryland's Medicaid expansion in January 2014). A differences-in-differences approach using logistic regression was used to investigate if differences between high and low utilizer cohorts changed from before and after the expansion.
  
  
  RESULTS
  During the study period, 726 (4.1%) out of 17,795 unique patients in 2013 and 380 (2.4%) of 16,458 during the same period in 2014 were high utilizers (p-value <0.001). ACSC-associated visit predicted being a high utilizer in 2013 (OR 1.66 (95% CI [1.37, 2.01])) and 2014 (OR 1.65 (95% CI [1.27, 2.15])) but this was not different between years (OR ratio 0.99, 95% CI [0.72, 1.38], p-value 0.97).
  
  
  CONCLUSIONS
  Although the proportion of high utilizers decreased significantly after Maryland's Medicaid expansion, ACSC-associated ED visits by high ED utilizers were unaffected.
authors.affiliation: Department of Emergency Medicine, University of Maryland, Baltimore, MD, USA. Electronic address: dgingold@umem.org.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Gingold
authors.affiliation: Department of Emergency Medicine, University of Maryland, Baltimore, MD, USA.
authors.forename: Rachelle
authors.initials: R
authors.lastname: Pierre-Mathieu
authors.affiliation: Department of Emergency Medicine, University of Maryland, Baltimore, MD, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Cole
authors.affiliation: Department of Emergency Medicine, West Virginia University, Morgantown, WV, USA.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Miller
authors.affiliation: Department of Emergency Medicine, University of Maryland, Baltimore, MD, USA; Baltimore City Health Department, Baltimore, MD, USA; Department of Emergency Medicine, Henry Ford Hospital, Detroit, MI, USA.
authors.forename: Joneigh S
authors.initials: JS
authors.lastname: Khaldun
mesh_terms: D000328:Adult; D000553:Ambulatory Care / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005249:Fees and Charges / Q000706:statistics & numerical data; D005260:Female; D006297:Health Services Accessibility / Q000706:statistics & numerical data* / Q000639:trends; D006801:Humans; D019458:Insurance Coverage; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008484:Medicaid / Q000706:statistics & numerical data*; D058991:Patient Protection and Affordable Care Act / Q000458:organization & administration / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology
keywords: Affordable Care Act; Ambulatory care sensitive conditions; ED utilization; Medicaid expansion