Table 3.

Some methods for external validation and the level of information about the derivation study they require

	Method	Aspect	Information
			L1	L2	L3
1	Regression on PI in validation data	D, F	$$✓$$	$$✓$$	$$✓$$
2	Check model misspecification/fit	F	$$✓$$	$$✓$$	$$✓$$
3	Measures of discrimination	D	$$✓$$	$$✓$$	$$✓$$
4	Kaplan-Meier curves for risk groups	D, C	×	$$✓$$	$$✓$$
5	Logrank/Cox tests between risk groups	D	×	$$✓$$	$$✓$$
6	Hazard ratios across risk groups	D	×	$$✓$$	$$✓$$
7	Calibration	C	×	×	$$✓$$

L1, L2 and L3 denote increasing amounts of information (see text). Key to Aspect: D, discrimination; C, calibration; F, model fit.