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?