Collecting unit cost data in multicentre studies

International comparisons of health care systems and services have created increased interest in the comparability of cost results. This study compared top-down and bottom-up approaches to collecting unit cost data across centres in the context of examining the cost-effectiveness of dialysis therapy across Europe. The study tested whether health care technologies in different countries can be costed using consistent and transparent methods to increase the comparability of results. There was more agreement across the approaches for peritoneal dialysis than for than haemodialysis, with differences, respectively of €91–1,687 vs. 333–7,314 per patient per year. Haemodialysis results showed greatest differences where dialysis units were integrated as part of larger hospitals. Deciding which approach to adopt depends largely on the technology. However, bottom-up costing should be considered for technologies with a large component of staff input or overheads, significant sharing of staff or facilities between technologies or patient groups and health care costing systems which do not routinely allocate costs to the intervention level. In these circumstances this costing approach could increase consistency and transparency and hence comparability of cost results.