Methods of Systematic Review Table 1 Five levels of evidence

Level

Research Design

Description

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

RCT

1 Higher Randomized Controlled Trial, PEDro score ≥ 6.

 

 

Level 2

RCT

 

Lower RCT, PEDro score < 6.

Prospective controlled trial

Prospective controlled trial (not randomized)

Cohort

 

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

Pre-post

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

 

Post-test

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

Observational

 

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

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