Multipoint linkage analysis under heterogeneity: incorporation of parametric and nonparametric approaches

Using a recently developed multipoint parametric method, which tests for linkage in the presence of heterogeneity, we performed a genome-wide search for linkage using the German asthma data. Both dominant and recessive models were assumed in this parametric approach. Identity-by-descent (IBD) sharing for affected sibs was also calculated to help identify an appropriate genetic model and localize the trait locus. The strongest evidence for linkage was on chromosome 6 (p-value = 0.00006) under the dominant model with heterogeneity. Using both linkage and IBD sharing information for D6S422 (36.55 cM) on chromosome 6, we conducted exploratory analyses to locate additional trait loci that might explain the linkage heterogeneity. We found evidence of heterogeneity between D6S422 and D11S4111 based on a test of association (p-value = 0.0015).