Model-based CART analysis based on the biomarker GP73 conditional on the tree analysis using AFP, AAT, Kininogen and age, after controlling for site, for the stratified male-only subset. For this subset, age alone, independent of other biomarkers, plays a significant role in the incidence of HCC (p < 0.001). The node pair (1,5) represents the sub-group of 29 men aged >65 that have a significantly higher incidence of HCC. The node pairs (1,2) and (2,4) represent the sub-group of 59 men aged 65 or younger for whom a higher AFP level (>1.48) is significantly associated with increased incidence of HCC (p = 0.001) irrespective of GP73 level. A detailed interpretation of this tree is provided in the text.