development process: establishing evidence foundations for and rating strength of recommendations, articulation of recommendations, external review, and updating.
Clinical practice guidelines (CPGs) fundamentally rest on appraisal of the quality of relevant evidence, comparison of the benefits and harms of particular clinical recommendations, and value judgments regarding the importance of specific benefits and harms. Historically, value judgments regarding potential outcomes have been made implicitly rather than explicitly, and the basis for judgments regarding the quality of evidence and strength of a recommendation has often been unclear. As a result, many CPG developers now apply formal approaches to appraising both the evidence quality and the strength of recommendations (Ansari et al., 2009; Schünemann et al., 2006a; Shekelle et al., 2010).
Although much has been written about the concept of “quality of evidence,” there continues to be considerable variability in what the term is used to describe. Ultimately the term “quality of evidence” is used to describe the level of confidence or certainty in a conclusion regarding the issue to which the evidence relates. And, historically, as detailed hereafter, the notion of quality has emphasized research design, so that evidence quality evaluations arose from the inherent rigor (e.g., RCT vs. uncontrolled case series) of study designs. This certainty or confidence is frequently expressed by assigning a score, rating, or grade (typically in the form of numerals, letters, symbols, or words) to the quality of evidence. Although critically important, it must be underscored that evidence quality as it often has been construed, is not the only factor that needs to be considered when drawing a conclusion regarding optimal clinical practice. Other considerations include the relevance of available evidence to a patient with particular characteristics; the quantity (i.e., volume and completeness) and consistency (i.e. conformity of findings across investigations) of available evidence; and the nature and estimated magnitude of particular impacts of an individual clinical practice and value judgments regarding the relative importance of those different impacts (Verkerk et al., 2006).