Effect of patient cost sharing in South Korea: ACG risk-adjusted differences in health care utilization and expenditures among national health insurance and medical aid enrollees, 2004--2005

Objectives. To determine whether the insurance status of an enrollee is related to the enrollee's probability of utilization and expenditures; the enrollee's choice of health care provider as the most frequent source of care; and the enrollee's hospitalizations for ambulatory care sensitive conditions (ACSCs), after controlling for potential confounders.;Methods. South Korean claims data from 2004 and 2005 were analyzed. Analyses control for demographic and case-mix risk factors of the study population. Common two-part econometric estimation techniques are used to test the relationship between insurance status and expenditures. A logit regression was used to examine whether the insurance status of patients is associated with the likelihood of having a hospital outpatient department (HOPD) as their most frequent source of care (MFSC). A multinomial logit was used to examine the relative risk of varying MFSC for individuals in different insurance programs. Finally, a logit regression was used to compare the likelihood of ambulatory care sensitive admissions (ACSAs) among patients using HOPDs as their MFSC for outpatient services with other patients receiving outpatient services from non-HOPDs.;Results. Compared to low-income National Health Insurance (NHI) enrollees, Medical Aid II (MA2) groups were not experiencing higher expenditures, while Medical Aid I (MA1) groups were experiencing higher expenditures. After adjustment, differences in expenditures by insurance status were diminished. Compared to the NHI counterparts, MA1 beneficiaries were more likely to use an HOPD as the MFSC, while MA2 beneficiaries were less likely to. MA1 and MA2 recipients who used an HOPD as their MFSC were more likely to be admitted for ACSCs than those who did not. Among those who used an HOPD as the MFSC, it was found that MA beneficiaries were more likely to have an ACSA.;Conclusions. Increased cost sharing to MA2 recipients would be expected to lead to less utilization and potentially negative effects on their health. Imposing cost sharing on MA1 groups would be a policy alternative for containing utilization and expenditures. Guiding MA patients to use sources of care other than HOPDs for ambulatory care services may lead to fewer ACSA.