Recalibration of time-varying covariate Cox model in external validation

Oregon Convention Center 

External validation is to validate a prediction model using external population data different from the original development cohort and often requires recalibration to preserve the accuracy of the model outcome prediction. Assessing the calibration of Cox model in external validation requires not only visualizing calibration plots but also testing the significant difference between the original model and recalibrated model with regard to the intercept and slopes. However, in the case of the Cox model, there is no intercept (γ0) to estimate. Alternative to the existing method of testing a logistic regression model (Vergouwe et al., 2017), γ0+ γ1 (Xβ ̂ ) for recalibrating and testing γ0=0 and γ1=1, we conducted a log-likelihood test of two models--calibration in-the-large (γ1=1) vs recalibrated (γ1 = γ ̃) models where γ ̃ is a new estimated coefficient and β ̂ are original coefficients of all risk factors, X. The study exemplifies these methods to externally validate the Veterans Affairs (VA) women cardiovascular disease (CVD) risk score to non-Veteran women--civilians and active-duty military service members.

External validation

Recalibration

Women

Cardiovascular Disease

Risk Score

Veterans 

Health Policy Statistics Section