Relative Weight Adjustment by Length of Stay for Thai Diagnosis Related Groups, Version 6.2

Abstract

Adjusted Relative Weight has been used with base rate for inpatient payment under Diagnosis Related Groups. This study explained how to derive the formula of adjusted relative weight for Thai Diagnosis Related Groups version 6.2. This descriptive study used inpatient data in 3 fiscal years (2014-2016) with 15,073,446 admissions. The majority of cases (79.2%) were inliers by length of stay (LOS), 2.2% high outliers, 3.2% low outliers, and 15.5% were short stays less than 24 hours in hospital. The average standard service charge of high outliers was the highest (50,412 baht per admission) and was the lowest (3,764 baht per admission) for cases stayed in hospital less than 24 hours. The LOS was significantly correlated with the standard service charge (r=0.721). The regression analysis of all cases gave the high adjusted R2 as 0.547 (the low outlier medical DRGs had adjusted R2 of 0.301, surgical DRGs adjusted R2 of 0.419, high outlier medical DRGs adjusted R2 of 0.628, and surgical DRGs adjusted R2 of 0.814). Four formula for adjusting relative weight based on LOS were formulated: (1) adjusted RW formula for inpatient who stay in hospital less than 24 hours (called RW0d) is calculated by dividing the average standard charge of each DRG by the average standard charge of all admissions; (2) adjusted RW for low outlier is calculated based on RW0d and pro rated LOS; (3) adjusted RW for high outlier is calculated based on regression coefficient (as cofactor). The new formula for caluculating AdjRW of Thai DRGs version 6.2 gave a 8.44% higher correlation with the standard service charge than the formula used in Thai DRGs version 5.1. Conclusion: The new formula for adjusting relative weight of the Thai DRGs version 6.2 was better than the formula used in the Thai DRGs version 5.1 in terms of having higher correlation with the standard service charge or treatment cost. However, more variables beyond LOS should be explored for adjusting RW in the next Thai DRGs version.