Methods of Systematic Review Table 1 Five levels of evidence


Research Design


Level 1a

Randomized Controlled Trial (RCT)

More than 1 Higher RCT: Randomized Controlled Trial, PEDro score ≥ 6. Includes within subjects comparison with randomized conditions and cross-over designs


Level 1b


1 Higher Randomized Controlled Trial, PEDro score ≥ 6.



Level 2



Lower RCT, PEDro score < 6.

Prospective controlled trial

Prospective controlled trial (not randomized)



Prospective longitudinal study using at least 2 similar groups with one exposed to a particular condition.

Level 3

Case control

A retrospective study comparing conditions, including historical controls

Level 4


A prospective trial with a baseline measure, intervention, and a post-test using a single group of subjects.



A prospective post-test with two or more groups (intervention followed by post-test and no re-test or baseline measurement) using a single group of subjects.

Case Series

A retrospective study usually collecting variables from a chart review.

Level 5



Study using cross-sectional analysis to interpret relations.

Expert opinion without explicit critical appraisal, or based on physiology, biomechanics or "first principles"


Clinical Consensus

Case Report

Pre-post or case series involving one subject