Once a suitable model for joint effects is determined, various alternative criteria can be used for evaluating utility for public health applications [Gail and Pfeiffer 2005]. The area under the receiver operating characteristics curves (AUC) is a popularly used measure for discriminatory ability. However, the measure is not necessarily a good guide in all applications. In particular, AUC is a measure that depends on the distribution of the risk-profile conditional on case-control status, and cannot take into account information about baseline risk of a disease, which could be an important determinant of degree of stratification for absolute risk. For example, a model with modest discriminatory performance, when applied to a relatively common condition such as breast cancer, was shown to provide sufficient stratification for absolute risk to be useful for weighing risks and benefits for a drug such as Tamoxifen [Gail, et al. 1999]. Studies that aim to develop risk models need to take into consideration specific public health applications and then accordingly use an appropriate criterion for evaluating utility of the models.
