Skip to main content

Table 1 Grading of the quality of the evidence based on the GRADE system

From: Safe prescribing of non-steroidal anti-inflammatory drugs in patients with osteoarthritis – an expert consensus addressing benefits as well as gastrointestinal and cardiovascular risks

Nature of evidence

Study design

Study execution

Consistency

Directness of evidence

A

Pairwise meta-analysis of comparative randomized controlled trials (RCTs) (for interventions)

No important flaws

Consistent

Direct or strong indirect

RCTs (for interventions)

Non-randomized studies (for diagnosis and prognosis)

B

Meta-analysis of RCTs or RCTs (for interventions)

Important flaw < OR > Inconsistent < OR > Weak indirect

Non-randomized studies (for diagnosis or prognosis)

Important flaw < OR > Inconsistent < OR > Weak indirect

Non-randomized controlled studies (for interventions)

No important flaws consistent direct < OR > Strong indirect

C

Non-randomized controlled studies (for interventions)

Important flaw < OR > Inconsistent < OR > Weak indirect

 

Meta-analyses or RCTs with a combination of important flaws AND inconsistency AND/OR indirect evidence

D

Other evidence (not expert opinion)

E

Expert opinion

Exceptions that can alter the quality of grading

Sparse data (few events); use of data not in its initial randomization or apparent publication bias can lower the quality; a very strong association can raise the quality

Coding notes

Important flaws occur when the highest standards of research that could be achieved by a study are not applied

Consistency occurs at two levels – design: consistent methods, patients, outcomes; and statistical: a test of homogeneity of a summary estimate when the level of design consistency is acceptable and meta-analysis appropriate

Directness – direct evidence: relevant patient benefits and harms are measured in studies; strong indirect: the surrogate endpoint is strongly related to desirable endpoints, or direct evidence is available for a sufficiently related patient group; weak indirect: the relationship between the study outcomes and patient benefits or harms is insufficient

Summary of quality of evidence

A. High quality of evidence – future evidence is unlikely to change confidence in the estimate of effect

B. Moderate quality of evidence – future evidence is likely to have an impact on the confidence of the estimate of effect and may change that estimate

C. Poor quality evidence – future evidence is very likely to have an impact on the confidence of the estimate of effect and is likely to change that estimate

D. and E. Very poor quality evidence – Any estimate of effect is very uncertain

  1. Developed from Lomas J, 1991 [71].