SOLAR also allows for the simultaneous analysis of multiple traits as well as the inclusion of multiple covariates. In the bivariate case, SOLAR estimates the proportion of variance in each phenotype that can be explained by a genetic locus as well as estimating the proportion of the genetic correlation between the phenotypes that can be explained by this locus. To ensure that reported linkage peaks were not the result of a small subset of pedigrees, homogeneity tests were performed using the SOLAR HLOD (Goring, 2002). This test contrasts a null model in which families belong to a single distribution exhibiting genetic linkage to the tested locus against an alternative model in which families belong to one of two distributions only one of which shows evidence of genetic linkage to the tested locus.
