PROSPECT levels of evidence and grades of recommendation

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) (

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


Consistent level 1 studies


Individual, randomised, controlled trials with statistically significant results


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


Systematic review (with homogeneity) of cohort studies


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


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


Outcomes research


Systematic review (with homogeneity) of case-controlled studies


Individual case-controlled study


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


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


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


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