Levels of evidence and grades of recommendation

Sources of evidence in PROSPECT

The evidence for prospect is derived from three separate sources, and this evidence is considered by the prospect working group to determine the prospect recommendations:

Procedure-specific evidence derived from the systematic reviews of the literature

Transferable evidence from comparable procedures identified by the members of the prospect Working Group

Current practice – A commentary on each of the interventions from the members of the prospect Working Group

Practical prospect recommendations are based on all the information

PROSPECT grades of recommendations

The recommendations of the PROSPECT Working Group are graded A–D, based on the level of evidence from the studies, which is in accordance with the Oxford Centre for Evidence-Based Medicine (CEBM website accessed Dec 2003, Sackett 2000) (see table below) (http://www.cebm.net)

In the context of PROSPECT, grades of recommendation are dependent on whether the evidence is from specific studies, transferable studies or clinical practice:

Specific evidence – grade A

Transferable evidence – grade B/C

Clinical practice – grade D

CEBM grades of recommendation

*Extrapolations: Data used in a situation that has potentially clinically important differences to the original study situation. In the case of PROSPECT, extrapolation largely refers to transferable evidence.

Study criteria

Level of evidence

Criteria for grading of recommendation

Grade of recommendation

Systematic review (with homogeneity) of randomised, controlled trials

1a

Consistent level 1 studies

A

Individual, randomised, controlled trials with statistically significant results

1b

All or none, i.e. prior to availability of new therapy, all died, now with therapy some survive; or, prior to therapy some died, now with therapy none die

1c

Systematic review (with homogeneity) of cohort studies

2a

Consistent level 2 or 3 studies (or extrapolations* from level 1 studies)

B

Individual cohort study (including low quality randomised controlled trial, e.g. <80% follow up)

2b

Outcomes research

2c

Systematic review (with homogeneity) of case-controlled studies

3a

Individual case-controlled study

3b

Case-series, and poor quality cohort and case-controlled studies

4

Level 4 studies (or extrapolations* from level 2 or 3 studies)

C

Expert opinion without explicit critical appraisal, or based on physiology, bench research or first principles

5

Level 5 evidence (or troublingly inconsistent or inconclusive studies of any level)

D

Levels of evidence and grades of recommendation Sources of evidence in PROSPECT The evidence for prospect is derived from three separate sources, and this evidence is considered by the prospect working group to determine the prospect recommendations: Procedure-specific evidence derived from the systematic reviews of the literature Transferable evidence from comparable procedures identified by the members of the prospect Working Group Current practice – A commentary on each of the interventions from the members of the prospect Working Group Practical prospect recommendations are based on all the information PROSPECT grades of recommendations The recommendations of the PROSPECT Working Group are graded A–D, based on the level of evidence from the studies, which is in accordance with the Oxford Centre for Evidence-Based Medicine (CEBM website accessed Dec 2003, Sackett 2000) (see table below) (http://www.cebm.net) In the context of PROSPECT, grades of recommendation are dependent on whether the evidence is from specific studies, transferable studies or clinical practice: Specific evidence – grade A Transferable evidence – grade B/C Clinical practice – grade D CEBM grades of recommendation *Extrapolations: Data used in a situation that has potentially clinically important differences to the original study situation. In the case of PROSPECT, extrapolation largely refers to transferable evidence.
Study criteria	Level of evidence	Criteria for grading of recommendation	Grade of recommendation
Systematic review (with homogeneity) of randomised, controlled trials	1a	Consistent level 1 studies	A
Individual, randomised, controlled trials with statistically significant results	1b
All or none, i.e. prior to availability of new therapy, all died, now with therapy some survive; or, prior to therapy some died, now with therapy none die	1c
Systematic review (with homogeneity) of cohort studies	2a	Consistent level 2 or 3 studies (or extrapolations* from level 1 studies)	B
Individual cohort study (including low quality randomised controlled trial, e.g. <80% follow up)	2b
Outcomes research	2c
Systematic review (with homogeneity) of case-controlled studies	3a
Individual case-controlled study	3b
Case-series, and poor quality cohort and case-controlled studies	4	Level 4 studies (or extrapolations* from level 2 or 3 studies)	C
Expert opinion without explicit critical appraisal, or based on physiology, bench research or first principles	5	Level 5 evidence (or troublingly inconsistent or inconclusive studies of any level)	D