[What can and cannot be achieved by registries : Perspective of the registry working group of the German Network of Health Services Research].

In addition to clinical trials, registries and cohort studies are the fundamental basis of patient-orientated research. The importance of registries is increasing because more questions involving patient care under routine conditions (real world data) need to be answered. This article supplies answers to the questions: what can be achieved with registries and what are the limitations? Starting with a consensus definition of a registry from the German Network of Health Services Research (DNVF), the question of existing registries was examined and it was concluded that there was a lack of transparency. Consequently, a registry of registries similar to clinical trials registries is urgently needed as well as an evaluation of the quality of existing registries. Criteria are deduced that allow an assessment of the quality of a registry and which comprehensive possibilities registries can provide are discussed in eight different areas of interest to clinicians. The limitations of registries compared to randomized clinical trials and cohort studies are emphasized and discussed in this article. In the future, the use of registry-based randomized clinical trials (RRCT) will allow data related to efficacy as well as to effectiveness to be collated.