Model AUC AIC
I) Single linear term 0.886 (0.882-0.889)* 37 944
IIa) Dummy variables on 5 categories 0.894 (0.891-0.897)* 35 364
IIb) Dummy variables on 4 categories 0.887(0.884-0.890)* 35 799
IIc) Dummy variables on 3 categories 0.876 (0.872-0.880)* 37 729
IId) Binary variables 0.854 (0.850-0.858)* 39 594
III) FP 0.901 (0.898-0.904) 35 054
IV) GAM 0.901 (0.898-0.905) 34 948

FP: Fractional Polynomials, GAM: smoothing splines in a Generalized Additive
Model
*p<0.0001 when compared to the generalized additive model
Table 2: Discrimination and model fit.