Stability of assessment results of autistic and non-autistic language-impaired children from preschool years to early school age.

The predictability, consistency in group means, and intra-individual stability of developmental quotients and performance IQs were assessed from preschool to school age for 71 autistic children and 71 non-autistic communication-handicapped children, matched on chronological age, sex and initial performance IQ/DQ. DQs/performance IQs at age 4 yrs were found to be highly correlated with performance IQ at age 10 yrs for both groups. Absolute difference scores and group means were also equivalent for both samples, with no difference in patterns of change or the relationship between performance IQ and language status, as measured on the PPVT. Differences between diagnostic groups occurred only for scores on the Vineland Social Maturity Scale and the relationship between these scores and IQ.