Healthcare utilization patterns and risk adjustment under Taiwan's National Health Insurance system.

BACKGROUND AND PURPOSE Some recent proposals for reform of Taiwan's National Health Insurance (NHI) system include risk adjustment mechanisms. However, there is a paucity of research on risk adjustment and its utilization in health insurance systems in Taiwan. The purposes of this study were to determine the healthcare utilization pattern and to develop a risk assessment model for capitation payments under NHI. METHODS The individual enrollment and medical expenditure data for 1996 and 1997 were obtained from the Bureau of NHI. A random sample of 360,037 beneficiaries was divided into two sub-samples: one for model building and one for validation. Linear regression was employed to estimate the relationship between each individual's 1997 total expenditure and risk adjusters, i.e., age, gender, prior years' medical spending, and catastrophic status. RESULTS The 10- to 14-years age group had the lowest total expenditure of $NT 3,055 ($US 1 = $NT 27.5 in 1996) in 1996, while the 65 years and over age group had the highest at almost 10 times more than the lowest. The distributions of total expenditure for both genders followed the familiar J-shaped curve. The average of the total expenditure of individuals with a catastrophic diagnosis was more than 17 times that of individuals without. Age and gender resulted in a predictive R2 of only 3.8% in the risk assessment model. By including prior total expenditure, the predictive R2 increased to 24.2%. Further addition of catastrophic status increased the predictability slightly to 25%. Prior outpatient expenditure predicted 72% of subsequent outpatient expenditure, but prior inpatient expenditure predicted only 3% of subsequent inpatient expenditure. CONCLUSIONS As in other countries, age and gender provided only limited predictability in risk assessment. On the other hand, prior outpatient expenditure in this study provided relatively superior predictability in risk assessment. Prudence is required when including prior utilization as a part of the risk assessment model in calculating capitation payments, as this may indirectly encourage unnecessary use of healthcare services.

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