Using the kidney failure risk equation to predict end-stage kidney disease in CKD patients of South Asian ethnicity: an external validation study

Table 5 Internal validation of models 5 and 6

Performance measure	Apparent performance	Optimism	Optimism-adjusted performance
*Model 5*
C-index	0.9313	0.0003	0.9310
Overall O/E ratio	1.025	0.002	1.023
Calibration intercept	0.276	0.00009	0.276
Calibration slope	1.025	0.010	1.015
Brier score	0.012	0.00004	0.012
Scaled Brier score (%)	31.3	0.27	31.0
*Model 6*
C-index	0.9339	0.0003	0.9336
Overall O/E ratio	1.04	0.003	1.04
Calibration intercept	0.249	0.002	0.247
Calibration slope	0.956	0.007	0.948
Brier score	0.011	0.00007	0.011
Scaled Brier score (%)	29.0	0.40	28.6

Internal validation completed via bootstrapping with 500 samples. The optimism-adjusted calibration slope can be applied as a uniform shrinkage factor to adjust the model coefficients. O/E observed/expected

ISSN: 2397-7523