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Updating the Assignment of Levels of Evidence

Marx, Robert G. MD; Wilson, Sean M. BA; Swiontkowski, Marc F. MD

Journal of Bone & Joint Surgery - American Volume: 7 January 2015 - Volume 97 - Issue 1 - p 1–2
doi: 10.2106/JBJS.N.01112

Associate Editor for Evidence-Based Orthopaedics


Orthopaedic surgeons, like all physicians, must make clinical decisions based on the best available evidence. This evidence comes from individual clinical experience and external sources1. Although clinical experience is left to the physician, the medical and surgical literature provides the best external evidence. To facilitate the process of determining the best evidence to answer a clinical question, The Journal of Bone & Joint Surgery assigns level of evidence (LOE) ratings to all clinical articles.

Since 20032, The Journal has used a hierarchical rating system based on the recommendations of the Centre for Evidence-Based Medicine (CEBM) in Oxford, United Kingdom, to rank articles according to the study design used to answer the primary research question3. In 2011, the CEBM updated its recommendations. After robust internal and external discussion, The Journal has decided to keep pace with the CEBM and has updated our LOE table.

The new LOE table emphasizes the clinical applications of research findings and encourages a more holistic assessment of study design and execution. Those familiar with the original table will notice that this update retains many features of its predecessor4. Nonclinical articles (such as cadaveric and animal studies) are still excluded from the ranking system, studies are still divided by type (therapeutic, prognostic, diagnostic, or economic analysis), and much of the ranking criteria remains the same.

Although the new table borrows from the original, it also represents an important departure. The most apparent change is structural. The rows and columns have been transposed, and there is an additional column for clinical questions. This new design reflects the order and the types of questions that arise in the process of clinical care. In this way, the table continues to provide a hierarchy of evidence, but it also assumes a new role, guiding busy clinicians to the best available evidence in real time. Whereas interaction with the original table was limited to authors and editors, the new table will engage readers more directly. Readers are encouraged to formulate their clinical question and to consult the table to determine how to conduct their search. For example, if a clinician asks, “does this intervention help?” the table will direct the reader to seek Therapeutic Level-I (randomized controlled trial) studies first, followed sequentially by Levels II (prospective cohort), III (retrospective cohort), and IV (case series). For clinicians who already perform literature searches in this fashion, the table’s increased accessibility will provide transparency to The Journal’s process of assigning LOEs.

Another important update is the table footnote that allows authors and editors to grade Level-I through IV studies upward due to “dramatic effect” or downward on the basis of “study quality, imprecision, or indirectness or because the absolute effect size is very small.” The criteria in the table still guide the process, but this increased flexibility allows for more appropriate LOE assignments when the decision is not obvious. It is also important to note that, although this table is based on CEBM recommendations, we chose not to follow CEBM’s policy of reserving the Level-I designation for systematic reviews. Systematic reviews are important, but we believe that high-quality original research merits an equally high LOE5. Additionally, The Journal recently published guidelines for the submission of systematic reviews and meta-analyses6.

Lastly, the section on “Economic and Decision Analyses” was eliminated from the CEBM table, but we have elected to include these studies, now referred to as “Economic” in our table, as they are very important in orthopaedic surgery. These research methodologies are performed with use of preexisting data. The quality of these data and the type of analysis affect the LOE7,8. In probabilistic sensitivity analysis, each realization of a parameter is drawn from a prespecified distribution. In stochastic sensitivity analysis, the parameter values are selected from plausible ranges, for example, within the 95% confidence interval of the point estimate.

We view the LOE system as a guide to help determine the robustness of research quality but caution that a higher LOE does not necessarily reflect the clinical importance of a given study. The reader is still responsible for examining each article critically and deciding what constitutes the best external evidence for his or her specific clinical question. The Journal publishes studies based on quality of evidence and clinical importance and will continue to take both into account.

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