Cost of diabetic eye, renal and foot complications: a methodological review.

INTRODUCTION: Diabetic retinopathy (DR), diabetic kidney disease (DKD) and diabetic foot ulcer (DFU) represent a public health and economic concern that may be assessed with cost-of-illness (COI) studies.

OBJECTIVES: (1) To review COI studies published between 2000 and 2015, about DR, DKD and DFU; (2) to analyse methods used.

METHODS: Disease definition, epidemiological approach, perspective, type of costs, activity data sources, cost valuation, sensitivity analysis, cost discounting and presentation of costs may be described in COI studies. Each reviewed study was assessed with a methodological grid including these nine items.

RESULTS: The five following items have been detailed in the reviewed studies: epidemiological approach (59 % of studies described it), perspective (75 %), type of costs (98 %), activity data sources (91 %) and cost valuation (59 %). The disease definition and the presentation of results were detailed in fewer studies (respectively 50 and 46 %). In contrast, sensitivity analysis was only performed in 14 % of studies and cost discounting in 7 %. Considering the studies showing an average cost per patient and per year with a societal perspective, DR cost estimates were US $2297 (range 5-67,486), DKD cost ranged from US $1095 to US $16,384, and DFU cost was US $10,604 (range 1444-85,718).

DISCUSSION: This review reinforces the need to adequately describe the method to facilitate literature comparisons and projections. It also recalls that COI studies represent complementary tools to cost-effectiveness studies to help decision makers in the allocation of economic resources for the management of DR, DKD and DFU.