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Evidence Rating:
The Strength of Recommendation Taxonomy
THE JOURNAL OF FAMILY PRACTICE uses a simplified rating system called the Strength of Recommendation Taxonomy (SORT). More detailed information can be found in the February 2004 issue, “Simplifying the language of evidence to improve patient care,” pages 111–120, or click here to access the article.
| Strength of recommendation |
Definition |
| A |
Recommendation based on consistent and good-quality patient-oriented evidence.* |
| B |
Recommendation based on inconsistent or limited-quality patient-oriented evidence.* |
| C |
Recommendation based on consensus, usual practice, opinion, disease-oriented evidence,* or case series for studies of diagnosis, treatment, prevention, or screening. |
Defining the terms
Disease-oriented outcomes: These outcomes include intermediate, histopathologic, physiologic, or surrogate results (eg, blood sugar, blood pressure, flow rate, coronary plaque thickness) that may or may not reflect improvements in patient outcomes.
Patient-oriented outcomes: These are outcomes that matter to patients and help them live longer or better lives, including reduced morbidity, mortality, or symptoms, improved quality of life, or lower cost.
Level of evidence: The validity of an individual study is based on an assessment of its study design. According to some methodologies,6 levels of evidence can refer not only to individual studies but also to the quality of evidence from multiple studies about a specific question or the quality of evidence supporting a clinical intervention. For simplicity and consistency in this proposal, we use the term level of evidence to refer to individual studies.
Strength of recommendation: The strength (or grade) of a recommendation for clinical practice is based on a body of evidence (typically more than 1 study). This approach takes into account the level of evidence of individual studies, the type of outcomes measured by these studies (patient-oriented or disease-oriented), the number, consistency, and coherence of the evidence as a whole, and the relationship between benefits, harms, and costs.
Practice guideline (evidence-based): These guidelines are recommendations for practice that involve a comprehensive search of the literature, an evaluation of the quality of individual studies, and recommendation grades that reflect the quality of the supporting evidence. All search, critical appraisal, and grading methods should be described explicitly and be replicable by similarly skilled authors.
Practice guideline (consensus): Consensus guidelines are recommendations for practice based on expert opinions that typically do not include a systematic search, an assessment of the quality of individual studies, or a system to label the strength of recommendations explicitly.
Research evidence: This evidence is presented in publications of original research, involving collection of original data or the systematic review of other original research publications. It does not include editorials, opinion pieces, or review articles (other than systematic reviews or meta-analyses).
Review article: A nonsystematic overview of a topic is a review article. In most cases, it is not based on an exhaustive, structured review of the literature and does not evaluate the quality of included studies systematically.
Systematic reviews and meta-analyses: A systematic review is a critical assessment of existing evidence that addresses a focused clinical question, includes a comprehensive literature search, appraises the quality of studies, and reports results in a systematic manner. If the studies report comparable quantitative data and have a low degree of variation in their findings, a meta-analysis can be performed to derive a summary estimate of effect.
Walkovers: Creating linkages with SORT
Some organizations, such as the CEBM, the Cochrane Collaboration, and the US Preventive Services Task Force (USPSTF), have developed their own grading scales for the strength of recommendations based on a body of evidence and are unlikely to abandon them. Other organizations, such as FPIN, publish their work in a variety of settings and must be able to move between taxonomies. We have developed a set of optional walkovers that suggest how authors, editors, and readers might move from 1 taxonomy to another. Walkovers for the CEBM and USPSTF taxonomies are shown in Table 4.
Many authors and experts in evidence-based medicine use the “Level of Evidence” taxonomy from the CEBM to rate the quality of individual studies. A walkover from the 5-level CEBM scale to the simpler 3-level SORT scale for individual studies is shown in Table 5.
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