Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?

We hope to find that the individuals included in the study are representative of the underlying population (and reflect the spectrum of illness). But, from what point in the target disorder should patients be followed? Above, we state 'usually early' implying an inception cohort (a group of people who are assembled at an early point in their disease), but clinicians may want information about prognosis in later stages of a target disorder. Thus, a study that assembled patients at a later point in the disease may provide useful information. However, if observations are made at different points in the course of disease for various people in the cohort, the relative timing of outcome events would be difficult to interpret. Thus, the ideal cohort is one in which participants are all at a similar stage in the course of the same disease.

Returning to the paper we found, the study included patients who were entered after their first stroke. Further details on entry procedures aren't included in the study.

1. Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?
2. Was patient follow-up sufficiently long and complete?
3. Were objective outcome criteria applied in a "blind" fashion?
4. If subgroups with different prognoses are identified:
   • Was there adjustment for important prognostic factors?
   • Was there validation in an independent group of "test-set" patients?