Table 4.
Issues in model developmenta
| Variables | Data |
|---|---|
| Sample size, median (IQR) | |
| Development cohortb | 2,562 (1,426 to 4,965) |
| Validation cohortsc | 1,895 (1,253 to 4,398) |
| Treatment of continuous risk predictors, n (%) | |
| All kept continuous | 13 (30%) |
| All categorised/dichotomised | 21 (49%) |
| Some categorised, some not | 6 (14%) |
| Unclear | 3 (7%) |
| Treatment of missing data, n (%) | |
| Not mentioned | 16 (41%) |
| Complete case | 21 (54%) |
| Multiple imputation | 1 (3%) |
| Other (for example, surrogate splitter for regression trees) | 1 (3%) |
| Model-building strategy, n (%) | |
| Stepwise, forward selection, backward elimination | 20 (51%) |
| All significant in univariate analysis | 2 (5%) |
| Other | 12 (31%) |
| Unclear | 5 (13%) |
| Overfitting mentioned or discussed, n (%) | 5 (13%) |
aIQR, interquartile range; bsample size not reported in four studies; csample size not reported in two studies and unclear in one study.