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Critical Appraisal of Research Articles: Prognosis

Questions to Ask

Is the study valid?

  • Is the sample representative?  Does the study clearly define the group of patients, and is it similar to your patients?  Were there clear inclusion and exclusion criteria?
    • Were patients recruited at a common point in their illness?
    • Did the study account for other important factors?
    • Is the setting representative?
  • Was follow-up long enough for the clinical outcome?
  • Was follow-up complete?
  • Were outcomes measured "blind"?

Are the results important?

  • What is the risk of the outcome over time? Three ways in which outcomes might be presented are:
    • as a percentage of survival at a particular point in time
    • as a median survival (the length of time by which 50% of study patients have had the outcome)
    • as a survival curve that depicts, at each point in time, the proportion (expressed as a percentage) of the original study sample who have not yet had the specified outcome
  • How precise are the estimates?


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Thomas Harrod
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