Evidence Hierarchy
A ranking system for the strength of different types of clinical evidence, from weakest to strongest: expert opinion, case reports, cohort studies, randomised controlled trials, systematic reviews and meta-analyses. The evidence hierarchy helps evaluate how much confidence to place in findings for any compound.
Technical Context
The traditional evidence pyramid (bottom to top): expert opinion/editorials, case reports/case series, cross-sectional studies, case-control studies, cohort studies, randomised controlled trials, systematic reviews/meta-analyses. Modern frameworks add nuance: GRADE (Grading of Recommendations Assessment, Development and Evaluation) rates certainty of evidence as high (further research unlikely to change confidence), moderate (further research likely to change confidence), low (further research very likely to change confidence), or very low (any estimate is very uncertain). GRADE considers: risk of bias, inconsistency across studies, indirectness (applicability), imprecision (wide confidence intervals), and publication bias. For peptide compounds, the evidence hierarchy helps contextualise claims: a research compound with only in vitro data (below case reports on the hierarchy) has fundamentally different evidence than an approved drug with multiple Phase III RCTs and systematic reviews.