BMC Medical Research Methodology

Table 4 Discrimination measures and hazard ratios evaluated in the derivation and validation datasets

From: External validation of a Cox prognostic model: principles and methods

Measure	Derivation data		Validation data
	Estimate	SE	Estimate	SE
Harrell c-index	0.673	0.009	0.658	0.016
Gönen & Heller K	0.655	0.008	0.645	0.015
Explained variation ( $R_{D}^{2}$ )	0.166	0.017	0.145	0.033
HR: group 2 versus 1	1.58	0.19	1.63	0.35
HR: group 3 versus 1	3.33	0.39	3.34	0.70
HR: group 4 versus 1	4.75	0.60	6.33	1.54

All values are based on the PI of the prognostic model. Risk groups were defined as described in the text. Standard errors (SE) for the c-index and for R D 2 were estimated from 200 bootstrap samples. HR = hazard ratio.

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