General Selection and Exclusion Criteria

Study type	- original studies - systematic reviews of sufficient quality:  - research question of systematic review corresponds (largely) to the basic question  - search is performed in at least 2 relevant databases, e.g. Cochrane Library, Medline/PubMed  - reporting of the complete search strategy  - no relevant keywords/search terms are missing
Follow-up period	- minimum follow-up period of 12 months for therapeutic or prognostic studies.
Exclusion criteria	- Case-reports - Expert opinion - Letters - Editorials - Case control studies for diagnostic tests - Narrative reviews