Economics in sample size determination for clinical trials.

In the design of clinical trials, sample size determination is usually undertaken by statisticians and clinicians. It is rare for health economists to be involved in this aspect of trial design. However, there are a number of outcome changes that are of 'economic significance', and it is important for trial designers and funders to be aware of these before planning, funding and mounting a trial. In this paper we demonstrate through the use of three examples (prevention of osteoporosis, management of infertility, and endometriosis) how economics can be used to influence the size of a clinical trial. Trials that are too small or too large waste research resources; health economics can lead to more efficient trial designs.