OBJECTIVES: The broadest definition of health costs includes the value of production losses. In France, the HAS considers a more restrictive perimeter and two perspectives depending on economic evaluations. The collective perspective (all payers including out-of-pocket expenses and costs for caregivers) is recommended for the efficiency model and the Health Insurance perspective for the budget impact model.

Our objective is to compare the sources used for the collection and the valuation of costs and thus measure the difference according to the perspective chosen.

METHODS: A review of the sources for each costs item available was carried out. Cost differentials for each item were presented in the context of prostate cancer treatment.

RESULTS: The assessment of main direct costs distinguishes resources consumed by the intervention (cost of acquisition and administration, cost of adverse events) and resources consumed by the care (follow-up care, care related to co-morbidities, care provided by carers, concomitant treatments, end-of-life care, etc.).

Two main sources of cost valuation are identified and recommended by the HAS: GHM cost data (from the national costs study) in collective perspective and GHM tariffs (from the PMSI) in Health Insurance perspective. However, these costs can come from a wide variety of sources, and the resulting estimates or methodological trade-offs need to be justified and discussed with experts on a case-by-case basis. These data are used to measure the opportunity cost of the innovation evaluated, making it a real challenge for medico-economic studies.

Nevertheless, this heterogeneity of sources has relatively little impact on the final results: for example, for a radiopharmaceutical treatment in prostate cancer, the cost differential between the two perspectives is only 9%.

CONCLUSIONS: Cost standardisation is a challenge for economic evaluation submitted in HAS. French Reference Unit Cost of Health‑care Services must be developed and shared.