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Levels of Evidence
NPTE Research & EBP
| Question | Answer |
|---|---|
| Systematic review | primary studies are summarized, appraised, and statistically combined |
| Randomized Controlled Trial | experimental study with random assignment with control group |
| Cohort study | prospective study, group with condition followed for defined time, comparison made to group without condition |
| Homogeneity | free of variations in the directions and degree of results between studies in SR |
| Case control study | Restrospective, group with condition compared with group without condition to determine factors that may have played a role in the condition. |
| Case report | only one individual studied in depth |
| Level 1a Level of Evidence | SR with homogeneity of multiple RCTs, randomization, lg # of pts, multicenter, substantial agreement in size and direction of treatment effects |
| Level 1b Level of Evidence | Individual RCT with narrow confidence level, treatment effects precisely defined |
| Level 1c | All or none case series. In absence of RCT, overwhelming evidence of substantial tx effect |
| Level 2a | SR with homogeneity of cohort studies |
| Level 2b | Individual cohort study or low quality RCT (small N) |
| Level 3a | SR with homogeneity of case-control studies |
| Level 3b | Individual case control study |
| Level 4 | Case series and poor quality cohort and case control studies, largely descriptive |
| Level 5 | expert opinion, observations not made on pts |
| CPG - clinical practice guideline | expert consensus, SR, meta analysis, assist practitioner for health care for specific clinical circumstances |