Cost determination and calculation
The costs generated during the diagnostic evaluation process of both units were analyzed based on a bottom-up approach (micro-costing) by which all services provided are collected exhaustively and corresponding prices are allocated. Micro-costing approaches stipulate all the resources spent in the provision of healthcare service [16,17]. The micro-costing analysis of this study was performed from the healthcare provider perspective and, for all included patients, relevant costs were obtained from the finance departments of the two hospitals.
The primary outcome variable of the study was the mean cost per patient. This cost was determined by summing all the single cost components that contributed to patient management until a diagnosis was made (i.e. from the first to the last visit). Personnel costs were calculated according to the staff time dedicated to each unit (clinicians, nursing, and administrative staff). These costs corresponded to the cumulative work time dedicated multiplied by the average hourly income of the staff category. The costs of diagnostic procedures including laboratory and pathology investigations, imaging examinations and endoscopies, and biopsy and cytology techniques were directly calculated using the unit cost of each test as provided by the respective finance departments. Direct costs attributable to specialist consultation and referral of patients were also incorporated. Indirect and structural costs were finally imputed to the computation. We determined the percentage distribution of direct, structural, and indirect costs relative to the mean total cost per patient. Another variable of interest for the study was the mean cost per visit. Neither costs borne by patients nor costs of referring agencies were included in the analysis. All costs were adjusted to the corresponding year (i.e. from January 2009 to December 2016) and were measured in Euros (\euro).