- Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?
- Was patient follow-up sufficiently long and complete?
- Were objective outcome criteria applied in a “blind” fashion?
- If subgroups with different prognoses are identified
- Was there an adjustment for important prognostic factors?
- Was there validation in an independent group of “test-set” patients?
Reference: Evidence-based Medicine – Sackett, Richardson, Rosenberg and Haynes.