Table 3. Comparison of results in 3 diferents external validation methods.

Calibration	Zhu’s Nomogram	K-fold	Leave-one-out	Bootstrap
R2	0.445	0.228-0.424	0.254-0.389	0.012-0.520
Brier	0.116	0.170-0.195	0.169-0.186	0.141-0.230
Discrimination
(ROC) Area under de curve	0.851	*	*	0.783

* ROC curve was performed for bootstrap only.