Quantitative Methods 2017

NTCP-models External validation • Different levels of adjustment (calibration-in-the-large, calibration of intercept and slope, model revision) – Closed testing procedure • Model extension: – Add new predictors to an existing model

Linear predictor: LP = + 1 X 1 + 2

X 2 X 2

LP = + 1

X 1

+ 2

+ 3new

X 3new

• Model adjustment / revision can still be considered as external validation, although the level of adjustment determines how new the model is

Vergouwe, et al. Stat Med 2017