Strength of Recommendations Taxonomy(SORT)
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Anum Ijaz M.B.B.S., M.D.[2]
Overview
The Strength of Recommendations Taxonomy (SORT) grades clinical evidence with a patient-centered focus, considering both the overall evidence and the quality of individual studies. It addresses the following three key elements of rating the strength of evidence:
- Quality: Assesses the validity of studies by minimizing bias.
- Quantity: Considers the number of studies and subjects involved.
- Consistency of Evidence: Evaluates the similarity of findings across studies on the same topic.
History
Multiple U.S. family medicine and primary care journals, including American Family Physician and The Journal of Family Practice, historically used diverse evidence-grading scales, creating confusion for readers. Over 100 different scales exist, and even the same letter grade (e.g., level B) may have different meanings across journals or articles. To address this, editors from key journals and the Family Practice Inquiries Network (FPIN) developed a unified taxonomy for the strength of recommendations.[1] This system was designed to:
- Be consistent across publications.
- Allow evaluation of both a body of evidence and individual studies.
- Cover screening, diagnosis, therapy, prevention, and prognosis.
- Remain simple and practical for authors, reviewers, editors, and clinicians.
Classification of Strength of Recommendations
| 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,* and case series for studies of diagnosis, treatment, prevention, or screening. |
*-Patient-oriented evidence measures outcomes that matter to patients: morbidity, mortality, symptom improvement, cost reduction, and quality of life. Disease-oriented evidence measures intermediate,physiologic or surrogate end points that may or may not reflect improvements in patient outcomes (e.g., blood pressure,blood chemistry,physiologic function,pathologic findings)[1]
Assessing Study Quality: Key Methods and Frameworks
The table below demonstrates how to evaluate whether a study measuring patient-oriented outcomes is of good or limited quality.
| Study Quality | Diagnosis | Treatment/Prevention/Screening | Prognosis |
|---|---|---|---|
| Level 1-good quality patient-oriented evidence |
|
|
|
| Level 2-limited quality patient-oriented evidence |
|
|
|
| Level 3-other evidence | Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series for studies of diagnosis, treatmnet, prevention, or screening. | ||
| SR= systematic review; RCT=randomized controlled trial. | |||
*-High-quality diagnostic cohort study: cohort design, adequate size, adequate spectrum of patients, blinding, and a consistent, well-defined reference standard. †-High-quality RCT: allocation concealed, blinding if possible, intention-to-treat analysis, adequate statistical power, adequate follow-up( greater than 80 percent). ‡-In all-or-none study, the treatment causes a dramatic change in outcomes, such as antibiotics for meningitis or surgery for appendicitis, which precludes study in a controlled trial.[1]
| Consistency across Studies | |
|---|---|
| Consistent |
OR
|
| Inconsistent |
OR
|
Applying Classification of Recommendation and Level of Evidence
Following two algorithms can be used to determine the strength of recommendations and level of evidence for an individual study respectively.
*Algorithm for determining the strength of a recommendation based on a body of evidence (applies to clinical recommendations regarding diagnosis, treatment, prevention, or screening). While this algorithm provides a general guideline, authors and editors may adjust the strength of recommendation based on the benefits, harms, and costs of the intervention being recommended. (USPSTF = U.S. Preventive Services Task Force).
The above two algorithms have been adopted from AAFP SORT Recommendation Scheme[1]
What Sets SORT Apart from Other Evidence-Based Taxonomies
- SORT takes into account the outcomes of a study, unlike other grading systems that focus only on a specific type of study (e.g., prevention or treatment) or are too complex.
- SORT clearly distinguishes between patient-oriented and disease-oriented evidence, which sets it apart from most other grading systems.
- SORT does not distinguish high- and low-quality observational studies like CEBM. Instead, it gives clear recommendations—strong (A), moderate (B), or weak (C)—for specific interventions. This approach is more practical, as there is no evidence that distinguishing observational study quality significantly alters clinical guidance.
Bridging Evidence Taxonomies: Navigating Between SORT and Other Grading Systems
Following tables provide information for authors, editors, and readers to transition between different taxonomies, with examples for Centre for Evidence-Based Medicine and British Medical Journal Clinical Evidence. shown below.[1]
| Suggested Walkovers Between Taxonomies for Assessing the Strength of a Recommendation Based on a Body of Evidence | ||
|---|---|---|
| SORT | CEBM | BMJ's Clinical Evidence |
| A. Recommendation based on consistent and good-quality patient-oriented evidence. | A. Consistent level 1 studies | Beneficial |
| B. Recommendation based on inconsistent or limited-qualiy patient-oriented evidence. | B. Consistent level 2 or 3 studies or pxtrapolations from level 1 studies. |
OR
|
| C. Level 4 studies or extrapolations from level 2 or 3 studies | Unlikely to be beneficial(recommendation against) | |
| C. Recommendation based on consensus, usual practice, disease-oriented evidence, case series for studies of treatment or screening, and/or opinion. | D. Level 5 evidence or troubling inconsistent or inconclusive studies of any level. | Unknown effectiveness. |
| SORT = Strength of Recommendation Taxonomy; CEBM = Centre for Evidence-Based Medicine; BMJ = BMJ Publishing Group. | ||
| Suggested Walkover Between the SORT and the CEBM Taxonomies for Assessing the Level of Evidence of an Individual Study | ||
|---|---|---|
| SORT Level | CEBM | |
| Treatment/Screening | ||
| 1 | Levels 1a to 1c | |
| 2 | Level 2 or 3 | |
| 3 | Level 4 or 5 and any study that measures intermediate or surrogate outcomes. | |
| Other Categories | ||
| 1 | levels 1 to 1c | |
| 2 | levels 2 to 4 | |
| 3 | level 5 and any study that measures intermediate or surrogate outcomes | |
| CEBM = Centre for Evidence-Based Medicine; SORT = Strength of Recommendation Taxonomy | ||
Resources
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Ebell MH, Siwek J, Weiss BD, Woolf SH, Susman J, Ewigman B, Bowman M (2004). "Strength of recommendation taxonomy (SORT): a patient-centered approach to grading evidence in the medical literature". J Am Board Fam Pract. 17 (1): 59–67. doi:10.3122/jabfm.17.1.59. PMID 15014055.