Table 5. Patient Financial Incentives.

Author (Year)	Design	Population	Cost Intervention	Effect on ED Use	Effect on Non-ED Use	Other Outcomes
Intervention: Copayment/Coinsurance
Hsu et al. (2006)39	Quasi-experimental, longitudinal, concurrent controls United States 1999–2001 Risk adjusted	Prepaid integrated delivery system, 19 medical center Intervention group: commercially insured, 2,257,445 patients (copayment levels: $0, $1–$5, $10–$15, $20–$35, and $50–$10 per ED visit) Control group: Medicare, with employer supplementation, 261,091 patients (copayment levels: $0, $1–$15, and $20–$50 per ED visit)	Comparison of various copayment levels over 36-month time period Copayment level chosen by employer, not patient	In commercially insured group, risk-adjusted RR of ED visit compared to no copayment group was 0.96 for $1–5 copayment group (CI = 0.96–0.97), 0.93 for $10–15 (CI = 0.92–0.94) 0.88 for $20–35 (CI = 0.87–0.89) 0.77 for $50–100 (CI = 0.76–0.77) In Medicare group, RR of ED visit compared to no copayment group was 0.97 for $1–15 copayment group (CI = 0.96–99) 0.96 for $20–50 (CI = 0.94–0.97)	Not reported	No significant change in hospitalizations, ICU admission, and deaths with higher copayment rates except the following: In commercially insured group, death rate was significantly higher in lowest copayment level of $1–$5 compared to no copayment with RR = 1.09 (CI = 1.02–1.16) In Medicare group, highest copay level ($20–$50) with decreased mortality rate (RR = 0.87, CI = 0.83–0.91)
Lowe et al. (2008)47	Before-and-after observational study United States 48 months	26 EDs, purposive sample of the state Intervention group: post–Oregon health plan cutbacks Control group: pre–Oregon health plan cut-backs Five groups of patients based on the class of payer: Commercially insured Oregon health plan Uninsured Medicare Others payers	Medicaid cutback, Oregon: the beneficiaries of the Oregon health plan receive new policy changes that include copayment for most of the health services (PCP visits, ED use, and hospitalization); decreased enrollment in health plan with increased number of uninsured patients	Oregon health plan 20% reduction in ED visits/month (CI = 13–18) Uninsured 20% increase in ED visits/month (CI = 13 to 18)	Not reported	Hospitalization from ED visit (adjusted ORs): Commercial 0.99 (CI = 0.95–1.04) Oregon health plan 1.09 (CI = 1.03–1.16) Uninsured 1.50 (CI = 1.39–1.62) Medicare 1.10 (CI = 1.06–1.13)
Lowe et al. (2010)40	Before-and-after study United States 2001–2004	State population study Intervention group: Medicaid enrollees with the standard plan Control group: Medicaid enrollees with the plus plan (not affected by cutbacks)	Medicaid cutback, Oregon: The beneficiaries of the Oregon health plan receive new policy changes that include copayment for most of the health services (PCP visits, ED use, and hospitalization and eliminated outpatient behavioral health services	Decrease in ED use rates (RR = 0.84; 95% CI = 0.83–0.86). Compared to Plus Plan members, use also decreased (RR = 0.82; 95% CI = 0.80–0.84) Injury-related visits also decreased (p < 0.001).	Not reported	ED visits leading to hospital admission also decreased: (RR = 0.83; 95% CI = 0.79–0.86). Compared to Plus Plan members, utilization also decreased (RR = 0.85; 95% CI = 0.82–0.89).
Mortensen (2010)48	Quasi experimental, pre–post design (differences-in-differences methodology) 24 months Risk adjusted	State-level study among Medicaid enrollees in 29 states. Intervention group: Medicaid enrollees in states with copayment increase (nine states) Control group: Medicaid enrollees in states without no copayment or no copayment change (20 states)	Medicaid ED visit copayment increase in nine states, ranging from $3 to $50	Significant increase in probability of any ED visits in a year (33.1 per person-month for change group vs. 24.7 for control group, p = 0.000)	Not reported	Not reported
O'Grady et al. (1985)41	Randomized controlled trial United States	State-level among six geographic areas in four states Intervention group: 3,973 persons were assigned randomly to different fee-for-service insurance plans with copayment rates of 0, 25, 50, or 95%	A coinsurance rate of 25, 50, or 95%—up to maximum of $1,000 as out-of-pocket costs	The probability of ED use among the copayment groups was fewer than the free group 25% copayment group fewer by 15% (p = 0.05) 50% copayment group fewer by 8% 95% copayment group fewer by 30% (p = 0.01) Individual-deductible plan fewer by 19% (p = 0.05) The ED use among the copayment groups was fewer than the free group 25% copayment group fewer by 21% (p = 0.01) 50% copayment group fewer by 18% 95% copayment group fewer by 35% (p = 0.01) Individual-deductible plan fewer by 20% (p = 0.05)	Not reported	The ED visit resulting in hospitalization among the copayment groups was fewer than the free group 25, 50, and 95% copayment groups fewer by 33% (p < 0.05)
Selby et al. (1996)42	Matched cohort study Risk adjusted	Group-model HMO, 15 medical centers Intervention group: 30,276 patients Control group: 60,408 patients (matched for age, sex, and location); second group 37,539 patients (matched for same + employer)	Introduction of a $25–$35 copayment for ED use in an HMO	Absolute decrease in ED usage by 28 visits/100 person-year in copayment group Risk-adjusted decrease in ED visits 14.6% more in copayment group than either control group (p < 0.001) Significant decreases in visits for less emergent conditions compared to emergent	No significant change in urgent care use and pediatric office visits over time between groups 4.4% decrease in rate of adult office visits in copayment group	Nonsignificant reduction in potentially avoidable hospitalizations in copayment group compared to control groups Significantly lower adjusted mortality rate in the copayment group (1.6/1,000) than in control group1 (2.2/1,000, p = 0.001) and control group2 (2.6/1,000, p = 0.06)
Wallace et al. (2008)43	Retrospective cohort study, difference-in-differences methodology United States 2001–2004	State population study, propensity score matched population Intervention group: Medicaid enrollees with the Standard Plan, 10,176 subjects Control Group: Medicaid enrollees with the Plus Plan, 10,319 subjects	Addition of $50 copayment for ED visits that did not result in admission. Intervention also included elimination of certain benefits (dental, mental health, etc.) as well as other copayments (outpatient visits, inpatient admissions, pharmacy, etc).	ED visits decreased by 7.9% (p = 0.03) in the standard (copayment) group relative to the plus group. ED visit expenditures by user increased 7.9% (p = 0.03) over the same time period despite the decrease In visits.	Pharmacy: decrease in use and expenditures (−2.2%, p < 0.001; −10.5%, p < 0.001). Inpatient: increase in use and expenditures (+27.3%, p < 0.001; +20.1, p < 0.001) Hospital outpatient: increase in use and expenditures (+13.5%, p < 0.001; 19.7%, p < 0.001) Ambulatory: decrease in use (−7.7%, p < 0.001) but increase in expenditures by user (+6.6%, p = 0.75)	Total expenditures (+2.2%, p = 0.47) by person unchanged despite overall reduction in use (−2.2%, p < 0.001)
Intervention: HDHP
Waters et al. (2011)45	Retrospective cohort study Risk adjusted	Major insurer in single state, propensity score matched sample Intervention group: 1,354 HDHP group initially in PPO, then switched and maintained in HDHP for all 3 study years Control group: 1,354 members of enrolled in PPO plan	HDHP with deductibles ranging from $1,700 to $6,000 vs. PPO plan. HDHP enrollees used standard PPO contracted amounts before meeting their deductible.	HDHP enrollees had lower probability of use and level of use (p < 0.05)	HDHP enrollees appeared to have decreased primary care use (p < 0.01), but greater specialty physician use (p < 0.05)	HDHP enrollees had significantly higher prescription drug utilization and expenditures (p < 0.05)
Wharam et al. (2007)44	Before-and-after study United States 2001–2005	Single-state, single-insurance carrier offering HDHP and HMO plans Intervention group: 8,724 enrollees with HDHP for at least 6 months, after 1 year of traditional HMO Control group: 59,557 enrollees with traditional HMO, matched on adult/child status.	Individuals in the HDHP group have annual individual deductibles ranging from $500 to $2,000. If the expenditure exceeds the deductible, individuals pay a copayment ($100) for each ED use. Individuals in the intervention group had copayment for each ED ($20-$100) and outpatient visit ($5–$25).	ED visits with 10.0% relative decrease (absolute change, 20.2 visits per 1,000) in the HDHP group compared with controls from baseline to follow-up (95% CI = −16.6% to −2.8%; p = 0.007)		ED visits resulting in hospitalizations with 24.7% relative decrease (with an absolute rate difference of −2.6% in the HDHP group (95% CI = −41.0% to −3.9%; p = 0.02) ED expense per HDHP member decreased from $75 in the baseline year to $36 in the follow-up period, an absolute decline of $52, representing a 58.5% relative decline (95% CI = −64.4% to −51.5%; p <0.001)
Intervention: Health Savings Account
Wilson et al. (2008)46	Multiyear cross-sectional study United States 2004–2006 Risk adjusted	Commercial insurance plan with both comprehensive major medical and CDHP Intervention group: enrollees of CDHP plan for the study year Control group: enrollees of traditional comprehensive major medical plan	CDHP includes a variety of products including health reimbursement accounts and health savings accounts, which are portable if an employee leaves his or her employer. All offer first-dollar coverage for preventive services.	After risk adjustment, CDHP plan members had 129.1 vs. 141.2 ED visits/1,000 members/year

CDHP = consumer-driven health plan; HDHP = high-deductible health plan; HMO = health maintenance organization; ICU = intesive care unit; PCP = primary care provider; PPO = preferred provider organization; RR = rate ratio.