Meta-analysis in medicine. Where we are and where we want to go.

An epidemiologically impeccable study does not bring answers to all the important questions. A structured and systematic integration of information from different studies of a given problem with a view to answering the original question or bringing additional information is the essence and objective of the meta-analytic approach to health problem solving. Original studies in medicine, being very heterogeneous in nature and structure require not only a quantitative approach (as in classical meta-analysis) but also an additional "qualitative meta-analysis" as well. The latter represents not only a systematic accumulation of both information and the characteristics of different studies, but also an assessment of quality, uncertainty, missing data, random error and bias across studies of interest. The greatest challenge of meta-analysis in medicine lies in the integration of the qualitative and quantitative assessment of given information (scoring of quality, weighing of the effect size by quality score, etc.). Meta-analysis in medicine must go beyond a simple pooling of data. It should become the "epidemiology of results of independent studies of a common topic of interest". Further development of meta-analysis in such an expanded way may have an important impact on decision-making in clinical medicine, and in health policies.