Table 1.

Levels of Evidence.

C2010 Levels of Evidence for Studies of Therapeutic Interventions

LOE 1: Randomized controlled trials (RCTs) (or meta-analyses of RCTs)

LOE 2: Studies using concurrent controls without true randomization (eg, “pseudo”-randomized)

LOE 3: Studies using retrospective controls

LOE 4: Studies without a control group (eg, case series)

LOE 5: Studies not directly related to the specific patient/population (eg, different patient/population, animal models, mechanical models, etc)

C2010 Levels of Evidence for Prognostic Studies

LOE P1: Inception (prospective) cohort studies (or meta-analyses of inception cohort studies), or validation of Clinical Decision Rule (CDR)

LOE P2: Follow-up of untreated control groups in RCTs (or meta-analyses of follow-up studies), or derivation of CDR, or validated on split-sample only

LOE P3: Retrospective cohort studies

LOE P4: Case series

LOE P5: Studies not directly related to the specific patient/population (eg, different patient/population, animal models, mechanical models, etc)

C2010 Levels of Evidence for Diagnostic Studies

LOE D1: Validating cohort studies (or meta-analyses of validating cohort studies) or validation of Clinical Decision Rule (CDR)

LOE D2: Exploratory cohort study (or meta-analyses of follow-up studies), or derivation of CDR, or a CDR validated on a split-sample only

LOE D3: Diagnostic case-control study

LOE D4: Study of diagnostic yield (no reference standard)

LOE D5: Studies not directly related to the specific patient/population (eg, different patient/population, animal models, mechanical models, etc)