Framework for assessing the internal validity of studies of prognosisa
| Study Feature | Qualities Sought |
|---|---|
| Patients | Recruited at a common point (usually early) in the course of the disease |
| Ideally complete (all eligible patients included) | |
| Source and selection of patients is explained | |
| Diagnostic and inclusion criteria well-described and defined | |
| Clinical and demographic characteristics fully described | |
| Follow-up | Sufficiently long to be meaningful |
| Outcome | Appropriate |
| Unbiased | |
| Assessed blinded to prognostic information | |
| Fully defined and known for all patients | |
| Candidate prognostic variables | Fully defined, including method of measurement |
| Available for all patients | |
| Analysis | Continuous predictors analyzed appropriately |
| Statistical adjustment for all important factors | |
| Treatments | Randomized or at least standardized |
| Fully described and explained |
a Modified from Altman.10