The second genome-wide linkage study included a total of 219 families. Both affected sib-pair and multigenerational families were genotyped.136 Suggestive evidence was observed for susceptibility loci on chromosomes 3q, 7p, 1q, 15q, and 6q. The strongest linkage evidence was obtained for markers on chromosome 3q27-28 when both definite and probable cases of OCD were considered affected. The maximum overall Kong and Cox LODall score (2.67) occurred with markers D3S1262 (P=0.0003) and D3S2398 (P=0.0004). The method proposed by Kong and Cox estimates the degree of allele sharing between affected individuals and provides using a maximum likelihood approach. When there is no linkage there should be no allele sharing greater than expected by chance.
