[Goals, possibilities and limits of quality evaluation of guidelines. A background report on the user manual of the "Methodological Quality of Guidelines" check list].

Recently a German appraisal instrument for clinical guidelines was published that could be used by various parties in formal evaluation of guidelines. An user's guide to the appraisal instrument was designed that contains a detailed explanation for each question to ensure that the instrument is interpreted consistently. This paper describes the purposes, format and contents of the user's guide, and reviews the key factors influencing the validity of guidelines. Taking into account international experiences, the purposes, chances and methodological limitations of a prospective assessment of clinical practice guidelines are discussed.