Estimates of the costs of implementing health interventions are required for informing a wide range of decisions in global health. Costs are used in economic evaluations, such as benefit-cost or cost-effectiveness analysis, and other economic analyses to inform priority setting. Cost interventions are also needed for financial planning and management, and the formulation of resource requirements and budgets. In addition, cost estimates can provide additional detail on how interventions are implemented, which can be useful for assessing the efficiency of service delivery.

Costs are typically estimated using a range of approaches and assumptions, often combining data obtained as part of research studies with data collected as part of routine program implementation. While numerous textbooks and guideline documents exist, analysts apply and interpret such guidance based on their prior training, professional experience, and context. However, there is no widely agreed-upon common guidance on principles, methods, and reporting standards specifically aimed at cost estimation across global health.

The variation in applying the methods and reporting of costs for global health interventions has long been recognized^1-3. This variation can have an impact on estimates of cost-effectiveness, which should be comparable across interventions^4,5. A review of economic evaluations in the Tufts Medical Center Cost-Effectiveness Analysis (CEA) Registry found a high level of variation in costing methods, although the review noted an improvement in consistency over time⁶. Differences in data collection methods and in the application of analytic methods, a general lack of comprehensiveness, and inconsistent compliance to existing guidance were all observed⁷. As a result, reviews of global health costs conclude that methodological heterogeneity and lack of transparency make it impossible to compare studies over setting and time^8-11, and several papers point to the need to develop standardized methods for cost estimation in global health¹².

The goal of the ‘Reference Case for Estimating the Costs of Global Health Services and Interventions’ is to improve the quality of cost estimates through improved consistency and transparency of methods, assumptions, and reporting. The Reference Case is a guide that helps ensure that the process of cost estimation is clearly conveyed and reflects best practices, so that those using cost data can interpret the findings properly and assess their quality (accuracy, precision, generalizability, and consistency). The Reference Case provides a practical framework for analysts to ensure that they consider how methods may influence estimates and thereby improve the interpretation and use of cost data.

The reference case approach has its origins in the field of economic evaluation. The first US Panel on Cost-Effectiveness in Health and Medicine (‘US Panel’) proposed the use of a reference case “to improve comparability of cost-effectiveness analyses designed to inform decision-making while allowing analysts the flexibility to design studies that answer issues specific to a particular problem or industry”. This concept has since been applied by the International Decision Support Initiative (iDSI) to economic evaluations in global health¹³ and was recently extended by the second US Panel¹⁴.

However, while these past guidelines include sections on costing, these sections focus primarily on reporting, and do not explicitly address the methods and processes behind cost estimation. Many countries do not yet provide routine data on costs, so primary data collection and estimation is required. Furthermore, cost data are required for more purposes than economic evaluation. This Reference Case should be complementary to the other Reference Cases, providing additional specification for those analysts who need to collect primary cost data.

The Reference Case presented here provides guidance on and encourages consistent adherence to core principles for evaluating intervention costs. The Reference Case structure adopts a “comply or justify” approach, which allows the analyst to adapt to the specific requirements of the costing exercise, but introduces the condition that judgments about methods choices are made explicitly and transparently. The principles are not intended to methodologically restrict or exclude novel methods to improve or expand cost estimation. Where methods are unclear or lack consensus, this Reference Case presents reasonable options for the analyst to consider, highlighting the strengths and weaknesses of each.

The Reference Case is designed to facilitate costing analyses, rather than adding onerous burdens on analysts. The Reference Case offers standards for the design, implementation, and reporting of cost estimates. It does not offer a comprehensive ‘how to’ guide, but we hope that the principles outlined here can inform the development of detailed costing manuals and tools, by our team and others. However, we do provide some tools, such as reporting tables, that can standardize and streamline the process of adopting the Reference Case principles.