Background: Variable quality of unit-cost data may lead to poor decision making due to biased results. Quality can relate to robustness, precision and reliability of the data, as well as standard reporting of cost methods and results. If quality of reporting is high, comparability across cost estimates and settings is enhanced. Conversely if reporting quality is low it is difficult to use cost estimates appropriately. In order to improve the nature and use of cost data in priority setting and decision making, understanding the quality of cost data and reporting can help to inform which methods need strengthening and what areas of reporting should be standardised. Findings from a review of cost methods and reporting will be used to guide the development of the reference case and improved methods for tuberculosis (TB) and HIV costing.

Methods: Eight electronic databases were systematically searched using key words relating to cost, TB and treatment. Next, we developed a comprehensive extraction tool, which allowed us to describe the methods used, appraise the quality and reporting standards of existing literature and extract tuberculosis costs. Inclusion and exclusion criteria were applied to establish those studies that contained primary cost data. Data was extracted on study scope, sampling, methods, inclusion of costs, valuation and analysis.

Results and discussion: We identified 21 293 records through our systematic search strategy. Of these, 775 papers met the inclusion criteria, with 252 articles containing empirically collected provider costs relating to TB. While the purpose of the costing studies was well defined, there was heterogeneity in the methods used to estimate costs, especially with respect to the reported discount rate and methods to measure and allocate costs.

Conclusions: A review of TB-costing studies indicates that transparency in methods is limited due to lack of standard reporting of methods and results, and in cases where methods are reported well, a variation in approaches for measuring costs. A reference case on costing may help encourage researchers to be explicit and transparent in how they estimate costs.