title: Cost-sharing for emergency care and unfavorable clinical events: findings from the safety and financial ramifications of ED copayments study.
abstract: OBJECTIVE
  To evaluate the effect of emergency department (ED) copayment levels on ED use and unfavorable clinical events. Data Source/Study Setting. Kaiser Permanente-Northern California (KPNC), a prepaid integrated delivery system.
  
  
  METHODS
  In a quasi-experimental longitudinal study with concurrent controls, we estimated rates of ED visits, hospitalizations, ICU admissions, and deaths associated with higher ED copayments relative to no copayment, using Poisson random effects and proportional hazard models, controlling for patient characteristics. The study period began in January 1999; more than half of the population experienced an employer-chosen increase in their ED copayment in January 2000.
  
  
  METHODS
  Using KPNC automated databases, the 2000 U.S. Census, and California state death certificates, we collected data on ED visits and unfavorable clinical events over a 36-month period (January 1999 through December 2001) among 2,257,445 commercially insured and 261,091 Medicare insured health system members.
  
  
  RESULTS
  Among commercially insured subjects, ED visits decreased 12 percent with the $20-35 copayment (95 percent confidence interval [CI]: 11-13 percent), and 23 percent with the $50-100 copayment (95 percent CI: 23-24 percent) compared with no copayment. Hospitalizations, ICU admissions, and deaths did not increase with copayments. Hospitalizations decreased 4 percent (95 percent CI: 2-6 percent) and 10 percent (95 percent CI: 7-13 percent) with ED copayments of $20-35 and $50-100, respectively, compared with no copayment. Among Medicare subjects, ED visits decreased by 4 percent (95 percent CI: 3-6 percent) with the $20-50 copayments compared with no copayment; unfavorable clinical events did not increase with copayments, e.g., hospitalizations were unchanged (95 percent CI: -3 percent to +2 percent) with $20-50 ED copayments compared with no copayment.
  
  
  CONCLUSIONS
  Relatively modest levels of patient cost-sharing for ED care decreased ED visit rates without increasing the rate of unfavorable clinical events.
authors.affiliation: Kaiser Permanente-Division of Research, 2000 Broadway, 3rd Floor, Oakland, CA 94612, USA.
authors.forename: John
authors.initials: J
authors.lastname: Hsu
authors.forename: Mary
authors.initials: M
authors.lastname: Price
authors.forename: Richard
authors.initials: R
authors.lastname: Brand
authors.forename: G Thomas
authors.initials: GT
authors.lastname: Ray
authors.forename: Bruce
authors.initials: B
authors.lastname: Fireman
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Newhouse
authors.forename: Joseph V
authors.initials: JV
authors.lastname: Selby
mesh_terms: D017047:Cost Sharing / Q000191:economics*; D003669:Deductibles and Coinsurance; D019033:Delivery of Health Care, Integrated / Q000191:economics; D004636:Emergency Service, Hospital / Q000191:economics* / Q000706:statistics & numerical data*; D006296:Health Services / Q000191:economics* / Q000706:statistics & numerical data*; D006302:Health Services Research; D006760:Hospitalization / Q000191:economics; D006801:Humans; D007348:Insurance, Health / Q000191:economics; D007362:Intensive Care Units / Q000191:economics / Q000706:statistics & numerical data; D008137:Longitudinal Studies; D009026:Mortality