Table 2 Levels of Evidence Definitions used for Descriptive Synthesis
Level of Evidence | Study Types |
|---|---|
Reviews (JBI, 2013) | |
 Level 1 | Level 1.a – Systematic review of Randomised Controlled Trials (RCTs) Level 1.b – Systematic review of RCTs and other study designs |
 Level 2 | Level 2.a – Systematic review of quasi-experimental studies Level 2.b – Systematic review of quasi-experimental and other lower study designs |
 Level 3 | Level 3.a – Systematic review of comparable cohort studies Level 3.b – Systematic review of comparable cohort and other lower study designs |
 Level 4 | Level 4.a – Systematic review of descriptive studies |
Studies (NHMRC, 2009) | |
 II | A randomised controlled trial |
 III-1 | A pseudorandomised controlled trial (i.e., alternate allocation or some other method) |
 III-2 | A comparative study with concurrent controls: ▪ Non-randomised, experimental trial ▪ Cohort study ▪ Case–control study ▪ Interrupted time series with a control group |
 III-3 | A comparative study without concurrent controls: ▪ Historical control study ▪ Two or more single arm study ▪ Interrupted time series without a parallel control group |
 IV | Case series with either post-test or pre-test/post-test outcomes |