Genome-wide linkage analyses using parametric and VC methods, both unadjusted and adjusted for sex and age, revealed several regions with LOD scores greater than 1.0. Chromosomes 2, 17, and 20 harbored peak LOD scores using both methods (though only in similar positions on chromosome 20). Follow-up of these chromosomes using multi-point MCMC analysis were consistent with the existence of QTLs on chromosomes 2 and 20. The most robust linkage result in our analyses was between 65 and 84 cM on chromosome 20 in the 20q13.1 region; results from sex- and age-adjusted analyses included peak two-point LOD scores of 1.30 (θ = 0.2, parametric) and 1.07 (heritability = 0.17, VC) at 70.51 cM (marker GATA47F05), a peak multi-point LOD score of 1.50 (heritability = 0.20, VC) at 84 cM, and an IR of 12.0 (MCMC) at approximately 65 cM. The trait distribution's non-normality may have affected accuracy of QTL detection, however, and no linkage result in this analysis was statistically significant.
