Although the markers identified under the two criteria, ALDX1 and ALDX2, are not entirely the same, several common regions were identified. The similarity of the regions supports some common genetic bases for ALDX1 and ALDX2, whereas the differences in the identified regions underscore the importance of using different phenotypes. As studied in [3,4], the methods using frailty models have correct type I error rates. The methods using frailty models incorporate age at onset and covariate factors and can increase the power of detecting linkage evidence over the traditional methods such as mean IBD test, which does not make use of age at onset information (Table 1). It is also interesting to note that the inclusion of smoking as a covariate in the linkage analysis resulted in more candidate genes with significant linkage evidence. We should note that the p-values reported here are not corrected for multiple comparisons.
