[What is "adherence to guidelines"? Theoretical and methodological considerations on a new concept for health system...

Adherence to guidelines denotes the degree of conformity between the knowledge, cognition and/or action of an agent with the recommendations of a guideline. Regarding this construct, an analysis of German and international publications of empirical research was conducted to reveal opportunities of operationalisation and measurement. The units of investigation of guideline conformity are actions. Analysis may focus upon agents (e.g., proportion of guideline-adherent specialists in a region), fields of action (e.g., percentage of guideline-adherent prescriptions or diagnostic procedures) or patients (percentage of patients treated according to the guideline). The construction of an appropriate instrument can follow an inductive or deductive approach, focusing either upon the reality of care or the relevant guideline(s) for the identification of candidate actions, decisions or guideline recommendations. The literature is dominated by percentage measurements of guideline conformity, the validity of which is limited to defined conditions. Conclusions for practice are only possible if one can distinguish between justified and non-justified non-adherence to guidelines. Evaluation of guideline adherence may contribute to an improvement of structural and process quality, the assessment of standards of practice and involved agents, and the improvement of guideline implementation. Whether guideline adherence is a valid surrogate parameter for the quality of care depends on the quality and appropriateness of the relevant guideline(s) and on the instrument used for measuring adherence. Guideline adherence does not prove that guidelines are used, but rather whether and to what extent the contents of guidelines are also contents of everyday care.