Evidence-Based Practice: Grading Evidence

Grading Evidence used in a Policy or Guideline

Clinical guidelines and procedures should be based on the best available evidence if it exists. Choosing the best study type to answer your question will assist you in finding the best evidence. 

The hierarchy pyramid for Primary Research :

Adapted from  NHMRC levels of evidence and grades for recommendations 2009

Level 1 evidence represents the gold standard for intervention studies. For some guidelines it may be appropriate to utilise results from studies with lower levels of evidence. Some clinical guidelines may also be informed by expert opinion in the field from within the Department of Health or nationally/internationally from journal articles. 

Once you have decided which articles best answer your question (See Finding the Evidence) you will then need to critically appraise the research. Some tools to help you with this can be found at 

• CEBM
• Joanna Briggs Institute 
• CASP

There are various frameworks available to grade the quality of evidence for making a recommendation thus providing a level of transparency for the guideline or procedure being developed:

• Centre for Evidence-Based Medicine, Oxford (1a-5)
• SORT: Strength-of-Recommendation Taxonomy (A,B,C)
• GRADE: Grading of Recommendations Assessment, Development and Evaluation (A,B,C,D)
• Practice Guidelines rating scales (various)