Meta-analysis and quality of evidence in the economic evaluation of drug trials.

Meta-analysis is an important part of assessing cost-effectiveness in that it may help determine which treatments are indeed effective and estimate the level of effectiveness of each. Meta-analysis uses the data from all the relevant trials and is a powerful tool for detecting effects too small to be picked up by individual trials. The assessment of quality of studies in a meta-analysis is critical, with priority needing to be given to high quality randomised studies. A written protocol, literature retrieval system, evaluation and selection criteria, choice of endpoints and ways to evaluate bias must all be pre-defined. Nevertheless, problems can arise when meta-analysis is used for cost-effectiveness analysis, due to variation in study medication protocols, duration of follow-up, and difficulties in interpreting patient subgroups and compliance. Despite being subject to the design flaws of both the trials analysed and the methods used in the analysis itself, meta-analysis provides a more objective and thorough means of evaluating effectiveness and hence the cost-effectiveness of treatments. Based on the meta-analysis evidence, we recommend that the current QALY league tables be split into an implementation table for clearly effective therapies, and a research priority table where the evidence of treatment effectiveness is less clear and more research is needed.