The usefulness of the Clinical Practice Guidelines depends on their quality. The AGREE II instrument for the evaluation of Guidelines and the GRADE system to rate the evidence and the strength of the recommendations.

The development of clinical practice guidelines (CPG) demands an extensive review and analysis of the available evidence. Using a systematic methodology is recommendable in order to write it up with the best quality possible. There are two tools that provide the framework used by many scientific organizations in the world: the AGREE instrument (Appraisal of Guidelines for REsearch & Evaluation) and the GRADE system (Grading of Recommendations Assessment, Development and Evaluation). The AGREE instrument works assessing key components of methodological quality of the guidelines, and intends to establish if the recommendations may be useful or not in clinical practice; the GRADE system categorises the quality of evidence and the strength of recommendations. In this paper the principles of each system are succinctly described, the objectives, methodology, and the sources for access.