Table 4 The GRADE System for Grading Quality of Evidence and Strength of Recommendations[2,5]
From: A system for rating the stability and strength of medical evidence
Quality of evidence for each outcome (high, moderate, or low) – based on the following criteria: |
   • Study design– grade of high or low assigned based on design (RCT = high, observational study = low) |
   • Study quality– Detailed study methods and execution. |
1) Limitations in quality can decrease grade one or two levels. |
2) Evidence of reporting bias can also decrease grade one level. |
3) Grade can be increased one level if all plausible confounders would have reduced the treatment effect. |
   • Consistency of results– The level of similarity of estimates of effects across studies. |
1) Important inconsistency can decrease grade one level. |
   • Directness of evidence– the extent to which the people, interventions, and outcome measures are similar to those of interest. |
1) Some or major uncertainty about directness lowers the grade one or two levels. |
   • Other considerations |
1) Magnitude of effect can increase the grade of evidence. Strong evidence of association (significant relative risk of >2 or <0.5 based on consistent evidence from 2 or more observational studies with no plausible confounders) increases the grade by one level. Very strong evidence of association (significant relative risk of >5 or <0.2 based on direct evidence with no major threats to validity) increases the grade by two levels. |
2) Evidence of a dose-response gradient increases the grade by one level. |
3) Imprecise or sparse data can lower the grade by one level. |
Relative importance of outcomes – included outcomes should be critical or important (but not critical) to a decision |
Overall quality of evidence – judged across outcomes based on the lowest quality of evidence for any of the critical outcomes |
Balance of benefits and harms – classified as net benefits, trade-offs, uncertain trade-offs, or no net benefits based on the important health benefits and harms |
Balance of net benefits and costs – are incremental health benefits worth the costs? |
Strength of recommendation – the extent to which one can be confident that adherence to a recommendation will do more good than harm |