Effect of costing methods on unit cost of hospital medical services.

OBJECTIVE To explore the variance of unit costs of hospital medical services due to different costing methods employed in the analysis. METHODS Retrospective and descriptive study at Kaengkhoi District Hospital, Saraburi Province, Thailand, in the fiscal year 2002. The process started with a calculation of unit costs of medical services as a base case. After that, the unit costs were re-calculated based on various methods. Finally, the variations of the results obtained from various methods and the base case were computed and compared. RESULTS The total annualized capital cost of buildings and capital items calculated by the accounting-based approach (averaging the capital purchase prices throughout their useful life) was 13.02% lower than that calculated by the economic-based approach (combination of depreciation cost and interest on undepreciated portion over the useful life). A change of discount rate from 3% to 6% results in a 4.76% increase of the hospital's total annualized capital cost. When the useful life of durable goods was changed from 5 to 10 years, the total annualized capital cost of the hospital decreased by 17.28% from that of the base case. Regarding alternative criteria of indirect cost allocation, unit cost of medical services changed by a range of -6.99% to +4.05%. We explored the effect on unit cost of medical services in one department. Various costing methods, including departmental allocation methods, ranged between -85% and +32% against those of the base case. Based on the variation analysis, the economic-based approach was suitable for capital cost calculation. For the useful life of capital items, appropriate duration should be studied and standardized. Regarding allocation criteria, single-output criteria might be more efficient than the combined-output and complicated ones. For the departmental allocation methods, micro-costing method was the most suitable method at the time of study. CONCLUSIONS These different costing methods should be standardized and developed as guidelines since they could affect implementation of the national health insurance scheme and health financing management.