Module 5: Evidence-Based Medical Practice

Levels of Evidence
Summary

Observational studies tend to overestimate treatment effects.
Hierarchy of evidence is not absolute.
If treatment effect is sufficiently large and consistent, then sometimes RCTs are appropriate. (Example: Pap smear screening virtually eliminates 100% of advanced cervical cancer in women who are screened appropriately. The evidence for performing PAP smears was all derived from retrospective cohort studies.)
A full description of the levels of evidence with definitions can be found at The Center for Evidence-Based Medicine. http://www.cebm.net/levels_of_evidence.asp


Modules	Module 5: Evidence-Based Medical Practice
Evidence-Based Medicine Forward Module Objectives Why Is EBM Important? Levels of Evidence What Is Evidence? Hierarchy of Evidence Systematic Review Systematic Review of Cohort Studies Summary The EBM Process Formulating a Clinical Question Purpose of Clinical Question Types of Clincal Questions The Well-Built Questions: PICO Searching for the Evidence Cochrane PubMed Helpful Tips Critically Appraise, Apply Evidence Resources Credits Return to Patient Safety & Quality Improvement	Levels of Evidence Summary Observational studies tend to overestimate treatment effects. Hierarchy of evidence is not absolute. If treatment effect is sufficiently large and consistent, then sometimes RCTs are appropriate. (Example: Pap smear screening virtually eliminates 100% of advanced cervical cancer in women who are screened appropriately. The evidence for performing PAP smears was all derived from retrospective cohort studies.) A full description of the levels of evidence with definitions can be found at The Center for Evidence-Based Medicine. http://www.cebm.net/levels_of_evidence.asp
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Levels of Evidence Summary