[Practical experience with overviews of reviews--valuable decision aid or academic exercise?]

The "overview of reviews" has evolved as a method to aggregate information from systematic reviews. Based on research projects conducted by two Austrian institutions, this article aims to point out methods and perceived strengths and limitations of overviews of reviews and to discuss their application and constraints for different healthcare settings. The six analysed projects differed in their objectives as well as in the corresponding methodology. We identified the following strengths of the overviews of reviews performed: the overview of the evidence base on an issue, the rapid detection of the results of numerous reviews, the demonstration of evidence gaps and potential savings in time and resources. At the same time, the methodology could lead to a loss of information, limited relevance and to uncertainties regarding the robustness of the overall results. However, the heterogeneity of the methods used shows that the development of methods for overviews of reviews is still ongoing. Whether overviews of reviews provide valuable decision support depends on the research question and realistic expectations towards the method.