Key conclusions (as determined by the work group) are supported by a conclusion grading worksheet that summarizes the important studies pertaining to the conclusion. Individual studies are classed according to the system presented below, and are designated as positive, negative, or neutral to reflect the study quality.
Conclusion Grades:
Grade I: The evidence consists of results from studies of strong design for answering the question addressed. The results are both clinically important and consistent with minor exceptions at most. The results are free of any significant doubts about generalizability, bias, and flaws in research design. Studies with negative results have sufficiently large samples to have adequate statistical power.
Grade II: The evidence consists of results from studies of strong design for answering the question addressed, but there is some uncertainty attached to the conclusion because of inconsistencies among the results from the studies or because of minor doubts about generalizability, bias, research design flaws, or adequacy of sample size. Alternatively, the evidence consists solely of results from weaker designs for the question addressed, but the results have been confirmed in separate studies and are consistent with minor exceptions at most.
Grade III: The evidence consists of results from studies of strong design for answering the question addressed, but there is substantial uncertainty attached to the conclusion because of inconsistencies among the results of different studies or because of serious doubts about generalizability, bias, research design flaws, or adequacy of sample size. Alternatively, the evidence consists solely of results from a limited number of studies of weak design for answering the question addressed.
Grade Not Assignable: There is no evidence available that directly supports or refutes the conclusion.
Study Quality Designations:
The quality of the primary research reports and systematic reviews are designated in the following ways on the conclusion grading worksheets:
Positive: indicates that the report or review has clearly addressed issues of inclusion/exclusion, bias, generalizability, and data collection and analysis.
Negative: indicates that these issues (inclusion/exclusion, bias, generalizability, and data collection and analysis) have not been adequately addressed.
Neutral: indicates that the report or review is neither exceptionally strong nor exceptionally weak.
Not Applicable: indicates that the report is not a primary reference or a systematic review and therefore the quality has not been assessed.
Classes of Research Reports:
- Primary Reports of New Data Collection:
Class A:
- Randomized, controlled trial
Class B:
Class C:
- Nonrandomized trial with concurrent or historical controls
- Case-control study
- Study of sensitivity and specificity of a diagnostic test
- Population-based descriptive study
Class D:
- Cross-sectional study
- Case series
- Case report
- Reports that Synthesize or Reflect upon Collections of Primary Reports:
Class M:
- Meta-analysis
- Systematic review
- Decision analysis
- Cost-effectiveness analysis
Class R:
- Consensus statement
- Consensus report
- Narrative review
Class X: