Studies on variability drivers of treatment costs in hospitals can provide the necessary information for policymakers and healthcare providers seeking to redesign reimbursement schemes and improve the outcomes-over-cost ratio, respectively. This systematic literature review, focusing on the hospital perspective, provides an overview of studies focusing on variability in treatment cost, an outline of their study characteristics and cost drivers, and suggestions on future research methodology.

We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Cochrane Handbook for Systematic Reviews of Interventions. We searched PubMED/MEDLINE, Web of Science, EMBASE, Scopus, CINAHL, Science direct, OvidSP and Cochrane library. Two investigators extracted and appraised data for citation until October 2020.

90 eligible articles were included. Patient, treatment and disease characteristics and, to a lesser extent, outcome and institutional characteristics were identified as significant variables explaining cost variability. In one-third of the studies, the costing method was classified as unclear due to the limited explanation provided by the authors.

Various patient, treatment and disease characteristics were identified to explain hospital cost variability. The limited transparency on how hospital costs are defined is a remarkable observation for studies wherein cost variability is the main focus. Recommendations relating to variables, costs, and statistical methods to consider when designing and conducting cost variability studies were provided.