level of evidence
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Introduction
A,B,C,D codes or ratings have been applied to recommendations of the USPSTF & other agencies
A:
- high-quality randomized controlled trial (RCT)*
- high-quality meta-analysis (quantitative systematic review)
B:
- nonrandomized clinical trial*
- nonquantitative systematic review
- lower quality RCT*
- clinical cohort study
- case-control study
- historical control
- epidemiologic study
C:
- consensus
- expert opinion
D:
* clinical trials are not practical for investigations concerning hazardous environmental substances
More general terms
References
- ↑ Siwek J et al, How to write an evidence-based clinical review article, Am Fam Physician 65:25, 2002