Are the best available clinical effectiveness data used in economic evaluations of drug therapies?

Abstract

Objectives: Use of evidence on clinical effectiveness that is of poor quality or is biased in favour of the therapy under study is a concern in economic evaluations and may contribute to a mistrust of pharmacoeconomic studies. This study aimed to determine whether the authors of economic evaluations use the best available evidence for clinical effectiveness.

Methods: One hundred economic evaluations of drug therapies (published in 2001–2003) were sampled randomly from the National Health Service Economic Evaluation Database, and the source of clinical evidence was identified. For each therapy, alternative, high quality sources of clinical effectiveness data were sought by searching the Database of Abstracts of Reviews of Effects and Health Technology Assessment databases. The magnitude and direction of the effect size in the different sources of evidence were compared.

Results: Relevant systematic reviews were found for only 32 of the 100 economic evaluations in the sample. In three cases these reviews had been identified by the authors of the economic evaluations and two of these cases were used in the evaluation. Comparisons were possible in 21 cases. The clinical effects reported in all 21 comparisons were similar in direction but differed in magnitude. Compared to the systematic reviews, the authors of economic evaluations used evidence that was more favourable in five cases, less favourable in four cases, and similar in 12 cases. Six of the economic evaluations and corresponding systematic reviews did not present measures of effectiveness in a manner that allowed comparison.

Conclusions: Authors of economic evaluations have not made sufficient use of the evidence available from systematic reviews of clinical effectiveness. The central role of economic evaluations in health policy makes it essential that improvements in economic methods are accompanied by a structured search for the highest quality information on clinical effectiveness.