During guideline development, researchers may retrieve and appraise several sources of primary and secondary literature. From these they derive recommendations that will be graded. The grade marked against a recommendation may vary according to the organization's method of grading: A, B, C or D or I, II, III, IV.
What’s most important to know is that recommendations graded A-B or I-II have been derived from studies associated with higher levels of evidence, because of a more rigorous study design. There is less bias* associated with the recommendation, and it is likely to be more valid than lower-graded recommendations. Therefore, any alterations to recommendations graded A-B are likely to affect the outcome of the guideline results.
“The grading does not emphasize the importance of the recommendation but relates to the strength of the supporting evidence.” (Scottish Intercollegiate Guideline Network, 2000)
*Bias is unknown or unacknowledged error created in the design, measurement, sampling, procedure or choice of problem studied. Our interpretation of research may be coloured by bias — by our outlook or personal viewpoint.
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Alphabetical Grading
Remember: “The grading does not emphasize the importance of the recommendation but relates to the strength of the supporting evidence.” (Scottish Intercollegiate Guideline Network, 2000)
Clinical grading recommendations may be graded in alphabetical format, as illustrated below:
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Grade
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Type of Recommendation (based on SIGN)
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A
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requires at least one meta-analysis, systematic review or Random Controlled Trial (RCT) rated as 1++ and directly applicable to the target population; or a systematic review of RCTs, or a body of evidence consisting principally of studies related at 1+, directly applicable to the target population and demonstrating overall consistency of results
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B
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requires a body of evidence including studies rated at 2++, directly applicable to the target population and demonstrating overall consistency of results; or extrapolated evidence from studies rated as 1++ or 1+
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C
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requires a body of evidence including studies rated as 2+, directly applicable to the target population and demonstrating overall consistency of results; or extrapolated from studies rated as 2++
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D
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evidence level 3 or 4; or extrapolated evidence from studies rated as 2+
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Numeric Grading
“The grading does not emphasize the importance of the recommendation but relates to the strength of the supporting evidence.” (Scottish Intercollegiate Guideline Network, 2000)
Clinical grading recommendations may be graded in Roman numeral format as shown below:
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Grade
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Type of Evidence
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I
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generally consistent finding in a majority of multiple acceptable studies
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II
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based either on a single acceptable study or a weak or inconsistent finding in multiple acceptable studies
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III
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limited scientific evidence that does not meet all the criteria of acceptable studies, or absence of directly applicable studies of quality broken down into components (III–A and III–B)
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III – A
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published expert opinion
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III – B
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unpublished expert opinion
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IV
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evidence is inadequate for recommendation
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Primary Care Toolkit
