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Evidence-Based Practice: Harm/Etiology

Critical Appraisal of Harm/Etiology Articles

1. Are the results of the therapy study valid?
  • Were there clearly defined groups of patients, similar in all important ways other than exposure to the treatment or other cause?
  • Were treatments/exposures and clinical outcomes measured in the same ways in both groups (was the assessemnt of outcomes either objective or blinded to exposure)?
  • Was follow-up of patients sufficiently long and complete?
  • Do the results satisfy some diagnostic tests for causation?
    • Is it clear that the exposure preceded the onset of the outcome?
    • Is there a dose-response gradient?
2. What are the results?
  • Did the study have a sufficiently large sample size?
  • How strong is the association between exposure and outcome?
    • Relative Risk:The ratio of the probability of developing, in a specified period of time, an outcome among those exposed to a risk factor, compared with the probability of developing the outcome if the risk factor is not present. 
    • Odds Ratio: The odds of the experimental group showing positive (or negative) effects of an exposure, in comparison to the control group.
  • How precise is the estimate of the treatment effect?
    • What are the confidence intervals?
3. Are the results relevant to your patient?
  • Are the study results applicable to the patients in your practice?
    • Are the study patients similiar to your own?
  • What is the magnitude of the risk?
  • Should you stop the exposure?

Harm/Etiology Critical Appraisal Worksheet

Harm/Etiology Statistics Calculators


Critical appraisal questions come from the following sources:
Guyatt, G. Rennie, D. Meade, MO, Cook, DJ.  Users’ Guide to Medical Literature: A Manual for Evidence-Based Clinical Practice, 2nd Edition 2008.
Sackett, DL, et al. Evidence Based Medicine: How to Practice and Teach EBM. 2nd ed. Edinburgh: Churchill Livingstone, 2000. BHSL Call Number: WB 102 E933 2000
Tips on Critical Appraisal of Evidence: Harm/Etiology. Centre for Evidence Based Medicine (Toronto)
Key concepts come from the following sources:
Glossary of Terms in The Cochrane Collaboration. (2005). Cochrane Collaboration. 
Evidence Based Medicine Toolkit: Epidemiology Glossary
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