An official ATS statement: grading the quality of evidence and strength of recommendations in ATS guidelines and recommendations.

Grading the strength of recommendations and the quality of underlying evidence enhances the usefulness of clinical practice guidelines. Professional societies and other organizations, including the American Thoracic Society (ATS), should reach consensus about whether they will use one common grading system and which of the numerous grading systems they would apply across all guidelines. The profusion of guideline grading systems confuses consumers of guidelines, and undermines the value of the grading exercise in conveying a transparent message. In response to this dilemma, the international GRADE working group has developed an approach that is useful for many guideline contexts, and that several national and international organizations have adopted. The GRADE system classifies recommendations as strong or weak, according to the balance of the benefits and downsides (harms, burden, and cost) after considering the quality of evidence. The quality of evidence reflects the confidence in estimates of the true effects of an intervention, and the system classifies quality of evidence as high, moderate, low, or very low according to factors that include the study methodology, the consistency and precision of the results, and the directness of the evidence. On recommendation of the ATS Documents Development and Implementation Committee, the ATS adopted the GRADE approach for its guidelines in line with many other organizations that have recently chosen the GRADE approach. This article informs ATS guideline developers, investigators, and those interpreting future ATS guidelines that follow the GRADE approach about the methodology and applicability of ATS guidelines and recommendations.