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[Searching clinical trials registries: procedure and documentation].

The identification of unpublished data is an important component in the assessment of drugs for a systematic review. This is why searching in clinical trials registries is indispensable. However, this type of search is not regularly conducted. At present, clinical trials registries that also contain results data are still seldom-used sources, which may be due to a number of reasons. On the one hand, there are a large number of clinical trials registries whose quality is difficult to judge sometimes; on the other hand, their heterogeneity and partly inadequate functionality such as, for example, the lack of export options, complicate searches of these sources. The present paper addresses the features of searches in clinical trials registries and describes the approach taken by the German Institute for Quality and Efficiency in Health Care (IQWiG). Initially, we describe the various types of registries and offer assistance with the selection of the clinical trials registries to be searched. A further focus lies on the description of the search procedure itself, as well as on the selection of the relevant registry entries and the documentation of this process in order to support those planning their own search in clinical trials registries.