Relationship between quality and source of evidence, levels of evidence and recommendation grade

Study quality assessments

Level of Evidence (LoE)

Grade of recommendation

(based on overall LoE, considering balance of clinical
practice information and evidence)

Study type

Statistical analyses and patient follow-up assessment

Allocation concealment

Jadad scores

Additional assessment of overall study quality required
to judge LoE

Systematic review with homogeneous results

N/A

N/A

N/A

N/A

1

A

Randomised controlled trial (RCT)

Statistics reported

and >80%

follow-up

AND

A

(1–5)

N/A

1

A

(based on two or more studies or a single large,
well-designed study)

OR

B

(3–5)

N/A

OR

B

(1–2)

Yes

Randomised controlled trial (RCT)

Statistics not reported or questionable or <80%
follow-up

AND/OR

B

(1–2)

Yes

2

B

(or extrapolation from one procedure-specific

LoE 1 study)

OR

C

(1–5)

N/A

OR

D

(1–5)

N/A

Non-systematic review, cohort study,

case study; (e.g. adverse effects)

N/A

N/A

3

C

Clinical practice information (expert opinion);
inconsistent evidence

N/A

N/A

4

D