The two most significant chromosomal regions (11p15.4-p15.3 with a 1-LOD interval of 19–26 cM and 15q13.3-q14 with a 1-LOD interval of 22–28 cM) in this study were also identified in several previous studies even though their signals were not as strong. Spence et al. (33) showed evidence for linkage to the same regions on chromosome 11 (20–55 cM with NPL scores > 2.0) using all ASD families and on chromosome 15 (20–25 cM with NPL scores > 1.5) using language-delayed families. Evidence for linkage was also reported for the chromosome 11 region (20–30 cM with Z scores > 3.0) in a study by Duvall et al. (28) using a quantitative trait from the Social Responsiveness Scale. Both of the above studies (28,33) used families from AGRE. In the present study, 132 (32%) of the ASD families with DelayedPhrase and 67 (21%) of the ASD families with IQ ≥ 70 were from AGRE. The exact number of overlapping families between our AGRE data and those in the two previous studies is unknown. To test if our linkage results were independent confirmation
