Simplifying the language of evidence to improve patient care: Strength of Recommendation Taxonomy : a patient-centered approach to grading evidence in the medical literature

Journal of Family Practice, Feb, 2004 by Mark H. Ebell, Jay Siwek, Barry D. Weiss, Steven H. Woolf, Jeffrey Susman, Bernard Ewigman, Marjorie Bowman

Key Points

* Several taxonomies exist for rating individual studies and the strength of recommendations, making the analysis of evidence confusing for practitioners.

* A new grading scale--the Strength of Recommendation Taxonomy (SORT)--will be used by several family medicine and primary care journals (required or optional), allowing readers to learn 1 consistently applied taxonomy of evidence.

* SORT is built around the information mastery framework, which emphasizes the use of patient-oriented outcomes that measure changes in morbidity or mortality.

* Levels of evidence from 1 to 3 for individual studies also are defined.

* An A-level recommendation is based on consistent and good-quality patient-oriented evidence; a B-level recommendation is based on inconsistent or limited-quality patient-oriented evidence; and a C-level recommendation is based on consensus, usual practice, opinion, disease-oriented evidence, or case series for studies of diagnosis, treatment, prevention, or screening.

Review articles (or overviews) are highly valued by physicians as a way to keep up-to-date with the medical literature. Sometimes though, these articles are based more on the authors' personal experience, or anecdotes, or incomplete surveys of the literature than on a comprehensive collection of the best available evidence. To improve the quality of review articles, there is an ongoing effort in the medical publishing field to use more explicit grading of the strength of evidence on which recommendations are based. (1-4)

Making evidence easier to understand

Several journals, including American Family Physician and Journal of Family Practice, have adopted evidence-grading scales that are used in particular articles. Other organizations and publications have also developed evidence-grading scales. The diversity of these scales can be confusing for readers. More than 100 grading scales are in use by various medical publications. (5) A level B recommendation in 1 journal may not mean the same firing in another. Even within 1 issue of a journal, evidence-grading scales often vary among the articles. Journal readers do not have the time, energy, or interest to interpret multiple grading scales, and more complex scales are difficult to integrate into daily practice.

Therefore the editors of the US family medicine and primary care journals (ie, American Family Physician, Family Medicine, Journal of Family Practice, Journal of the American Board of Family Practice, and BMJ-USA) and the Family Practice Inquiries Network (FPIN) came together to develop a unified taxonomy for the strength of recommendations based on a body of evidence. The new taxonomy should fulfill several objectives:

* Be uniform in most family medicine journals and electronic databases

* Allow authors to evaluate the strength of recommendation of a body of evidence

* Allow authors to rate the level of evidence for an individual study

* Be comprehensive and allow authors to evaluate studies of screening, diagnosis, therapy, prevention, and prognosis

* Be easy to use and not too time-consuming for authors, reviewers, and editors who may be content experts but not experts in critical appraisal or clinical epidemiology

* Be straightforward enough that primary care physicians can readily integrate the recommendations into daily practice.

Defining terms of evidence

A number of relevant terms must be defined for clarification.

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.