Strengths and Limitations of the Evidence

To access the full published Living Concussion Guidelines protocol, click on the following link: Protocol for a living systematic review for the management of concussion in adults

Individual Documents

A variety of validated tools are being used to evaluate individual documents. The following tools are included with very minor modifications (scoring in parentheses):

  • Downs and Black Scale for healthcare interventions (/28)
  • An amalgamation of items adopted from the Joanna Briggs Institute (JBI) critical appraisal tools for observational studies (/16)
  • Critical Appraisal Skills Programme (CASP) for qualitative studies (/9)
  • A MeaSurement Tool to Assess Systematic Reviews (AMSTAR 2) for systematic reviews (/20)
  • Appraisal of Guidelines for REsearch and Evaluation (AGREE II) for clinical practice guidelines (23 items each scored on a scale ranging from 1 (strongly disagree) to 7 (strongly agree))

*It is important to note that some evidence used to inform the Guideline for Concussion/Mild Traumatic Brain Injury and Persistent Symptoms: 3rd Edition is also retained for this guideline. Therefore, some of the tools used to evaluate these older studies may not match the list above. We also had originally used the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist for observational studies. However, we transitioned to the JBI critical appraisal tools in order to be more consistent with best practices.


Body of Evidence Aggregated Across Documents

For each recommendation, the aggregate of evidence informing that recommendation is also evaluated. This evaluation is done using the two methods outlined below.


Levels of Evidence

The following revised levels of evidence have been modified from the Guideline for Concussion/Mild Traumatic Brain Injury and Persistent Symptoms: 3rd Edition:

A = Recommendation supported by a moderate to high quality systematic review, or a high quality randomized controlled trial with appropriate control group.

B = Recommendation supported by other systematic reviews, longitudinal studies that have a control group, case control studies, well-designed single subject experimental designs, or low quality/small sized randomized controlled trials.

C = Recommendation supported primarily by expert opinion based on their experience, though uncontrolled longitudinal studies without control groups and cross-sectional studies are also classified here.



A slightly modified Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach is being used to rate the overall quality of relevant evidence. There are four possible quality labels: very low, low, moderate, and high. These labels are visually represented by the number of stars associated with each recommendation (i.e., one star equals “very low quality”, etc.). Each recommendation is also rated as being strong or weak based on a cost/benefit analysis.

*It is also important to note that, in order to be conservative, recommendations informed by only a systematic review are graded as “very low quality” because the individual studies informing the review are not evaluated by our guideline development team using our established methods. Therefore, there may be apparent discrepancies between Levels of Evidence and GRADE in some instances (e.g., a recommendation may be “Level A” but receive a GRADE of “very low quality”).

Please view the following GRADE protocol for more information and explanation:

Grade protocol.pdf


*A document will be posted here in the near future containing levels of evidence and GRADE information for each recommendation.