Table 1 Study variables and operational definitions

Sex

Male or female.

Age

Based on the World Health Organization definition and divided into dependent and non-dependent populations for a total of four groups: teenagers, 18–24 years; young adults, 25–44 years; adults, 45–64 years; and older adults, 65 years or above.

Diagnosis code

Inpatient diagnosis based on the declaration of inpatient payment regulated by the Bureau of National Health Insurance (BNHI); one principal diagnosis and four secondary diagnoses max. Total number of diagnoses.

Procedure code

Procedure based on the declaration of inpatient payment regulated by the BNHI; one principal procedure and four procedures maximum. Total number of procedures.

DRG fixed cost (R)

1. Tw-DRGs fixed payment = relative weight (RW) × standard payment rate (SPR) × (one basic treatment weight + pediatric weight + CMI weight + hospitals in mountainous region and offshore island weight)

2. Verification declaration for the lower limit of payment

3. Upper limit of payment = Tw-DRGs fixed payment*0.8

Estimated medical cost (R ₁ )

Total costs calculated by the corresponding NHI payment standard for treatment provided.

Cost difference (∆R)

Fixed cost, R – estimated medical cost, R ₁

Ratio of cost difference over fixed cost (∆R/R)

(Fixed cost, R – estimated medical cost, R ₁ )/DRG fixed cost