Types of Studies
Clinical Question/Best Level of Evidence
Type of Clinical Question |
Suggested Level of Evidence |
|
Therapy |
RCT > cohort > case control > case series |
|
Diagnosis |
Prospective, blind comparison to a gold standard |
|
Etiology/Harm |
RCT > cohort > case control > case series |
|
Prognosis |
Cohort study > case control > case series |
|
Prevention |
RCT > cohort study > case control > case series |
|
Clinical Exam |
Prospective, blind comparison to gold standard |
|
Cost |
economic analysis |
Questions of therapy, etiology, and prevention, which can best be answered by a RCT, can also be answered by a meta-analysis or systematic review.
The hierarchy of evidence is often presented as a pyramid, ranking study types based on their research methods, with systematic reviews and meta-analyses at the top, and expert opinion and anecdotal experience at the bottom.