Level 1

Randomized controlled trial (RCT)

Randomized controlled trial, PEDro score ³ 6.  Includes within subjects comparison with randomized conditions and cross-over designs

Level 2

RCT

Randomized controlled trial, 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.

Clinical Consensus

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

Case Report

Pre-post or case series involving one subject