de Godoi Rezende Costa Molino C, et al. - Via searching MEDLINE, Embase, the Cochrane Library, and 12 websites, researchers systematically evaluated 421 clinical practice guidelines (CPGs) for the management of common noncommunicable diseases in primary care using the validated Appraisal of Guidelines for Research and Evaluation Instrument, version II (AGREE-II) tool and clarify the factors correlated with quality of CPGs. The quality of CPGs in primary care is highly variable; less than 25% of the included CPGs are classified as high. Findings suggested an association of high-quality CPGs with a larger number of authors, governmental institutions, and the report of funding. Among included CPGs, year of publication, region, guideline version and scope were not linked to quality. The region of origin was not associated with the quality of CPGs, which suggests that it should be an international concern to improve the quality of CPGs.