Analyses of cost data in economic evaluations conducted alongside randomized controlled trials

The adoption and diffusion of new medical treatments depend increasingly on evidence of costs and cost-effectiveness. This evidence is increasingly being generated from economic data collected in randomized clinical trials. The objective of this article is to evaluate the statistical methods used for analysis of cost data in economic evaluations conducted alongside randomized controlled trials.

Systematic review of economic evaluations based on patient-level cost or resource-use data collected in randomized trials was published in 2003. One hundred fifteen articles were identified from the MEDLINE database. The use of statistical methods for 1) joint comparison of costs and effects and assessment of stochastic uncertainty, 2) incremental cost estimation, and 3) handling of incomplete or censored cost data was evaluated.

Only 42 (37%) of the 115 economic evaluations presented a cost-effectiveness ratio or estimated net benefits and 24 (57%) of these reported the uncertainty of this statistic. A comparison of costs alone was more common with 92 (80%) of the 115 studies statistically comparing costs between treatment groups. Of these, about two-thirds (62; 68%) used at least one statistical test appropriate for drawing inferences for arithmetic means. Incomplete cost data were reported in 67 (58%) studies with only two using a published statistical approach for handling censored cost data.

The quality of statistical methods used in economic evaluations conducted alongside randomized controlled trials was poor in the majority of studies published in 2003. Adoption of appropriate statistical methods is required before the results from such studies can consistently provide valid information to decision-makers.