Allele sharing methods or trait-model-free approaches provide a robust technique for linkage detection between a trait and a set of marker loci using pedigree data. The objective is to evaluate the departure from the null hypothesis of no linkage between the trait and the markers. The methods involve studying the extent of joint inheritance of the trait and marker alleles identical by descent (ibd) among related individuals in pedigrees. Many ibd allele-sharing approaches have been developed for small pedigrees, but for moderate or large pedigrees, they either do not make efficient use of pedigree information or else become computationally intractable.

I will discuss the limitations in current approaches and suggest a new statistic that makes more efficient use of the available data and a computationally efficient testing procedure to test for linkage. These methods will be presented together with a comparison of the proposed and existing approaches. Examples of application on both simulated and real data will be presented.