Individuals typically received at least two of three evaluations for autism symptoms: ADI-R, ADOS and clinical evaluation. Of the 1,679 affected individuals from 1,443 families, 966 met criterion for autism on the ADI-R and ADOS and most of these also had a clinical evaluation of autism; 160 affected individuals met criteria for autism on one of the two diagnostic instruments (ADI-R, ADOS) but were missing information on the other instrument; and, 553 individuals met criteria for spectrum disorder on one or both instruments. Affected individuals were recruited from both simplex and multiplex families, 71% of this sample being from multiplex families. The majority of the families were of European ancestry (83%).
