Hospital selection for unit cost estimates in multicentre economic evaluations - Does the choice of hospitals make a difference?

Objective: The objectives of this study were (i) to develop a conceptual fr amework for selecting hospitals for unit cost estimates in national and int ernational multicentre trials and (ii) to test the impact of alternative ho spital selection on the cost results. Design and setting: Within the conceptual framework, the following consider ations which can be used when selecting a sample of hospitals for unit cost estimates in multicentre trials were identified: the number of hospitals; the sampling method; and the desired level of geographical subanalysis. Results from a recently completed international multicentre trial were used to explore changes in cost results obtained by using alternative methods o f selecting and stratifying hospitals for unit cost estimates. Patients and participants: The study included 5041 women from 72 hospitals in 6 countries with prelabour rupture of the membranes at term. Interventions: The women were randomly assigned to induction of labour with intravenous oxytocin, induction of labour with prostaglandin E-2 gel, or e xpectant management for up to 4 days with labour induced if complications d eveloped. Main outcome measures and results: Across each of the 4 management strategi es of the study, the method of selecting and stratifying hospitals resulted in a 30 to 55% difference between the lowest and highest median unit cost estimates. In some cases, the relative ranking of the least to most expensi ve strategy varied across methods of hospital selection. The statistical co mparisons across strategies found that the method used had a substantial im pact on the conclusions of the economic evaluation. Conclusions: Unit cost information should be collected from as many hospita ls as possible. Multivariate hospital cost studies are needed to identify i mportant cost drivers that will assist with hospital selection in the futur e.