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?