Table 2.
Summary of study classification system
| Study rating | # | Study types |
|---|---|---|
| Prognostic studiesa (n=50) | ||
| PROG-1 | 14 | Retrospective analysis with multivariate model of multiple clinical trials, systematic review, or meta-analysis. |
| PROG-2 | 9 | Retrospective analysis with multivariate model of single larger trial (n≥200 for a two-arm study; n≥300 for a three-arm study). |
| PROG-3 | 11 | Retrospective analysis with multivariate model of single smaller trial (n<200 for a two-arm study; n<300 for a three-arm study). |
| PROG-4 | 16 | Retrospective analysis with multivariate model of observational study. |
| Predictive studiesb (n=4) | ||
| PRED-1 | 0 | Factor validation study prospectively designed to assess a predictive factor (as described in Sargent et al5). |
| PRED-2 | 4 | Retrospective analysis of clinical trial(s) with multivariate model plus formal test of interaction (including systematic review or meta-analysis reporting interaction test). |
| PRED-3 | 0 | Retrospective analysis of clinical trial(s) with multivariate model without formal test of interaction. |
| PRED-4 | 0 | Retrospective analysis with multivariate model of observational study, with or without formal test of interaction. |
Notes: PROG-1–5 and PRED-1–5 represent a rating system for prognostic and predictive studies, respectively, where one is high and five is low.
a
Fifty studies focused on prognostic factors (six of which focused on both prognostic and predictive factors). Nine PROG-5 studies excluded from final analyses (no regression modeling or only a univariate model).
b
Four studies focused exclusively on predictive factors. Two PRED-5 studies excluded from final analyses (no regression modeling or only a univariate model).
Abbreviation: #, number of studies.