Measuring pervasive developmental disorders in children and adolescents with mental retardation: a comparison of two screening instruments used in a study of the total mentally retarded population from a designated area.

The performance of two screening instruments for Pervasive Developmental Disorders was studied in the total population of participants with mental retardation between 4 and 18 years (n = 1059) in Friesland, a northern province of the Netherlands. Parents completed the Autism Behavior Checklist (ABC), staff completed the Scale of Pervasive Developmental Disorder in Mentally Retarded Persons (PDD-MRS). The screening instruments were related to the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule-Generic for 184 participants. The agreement between ABC and PDD-MRS was fair (kappa = .24). The ABC had a better criterion-related validity compared with the Autism Diagnostic Interview-Revised, and the PDD-MRS compared to the Autism Diagnostic Observation Schedule-Generic. However, related to the clinical classification, both instruments performed equally well. Concluding, the ABC and PDD-MRS partially identify the same cases related to external criteria. In addition, each instrument has its own contribution. Both instruments are valuable in detecting children who are at high risk for PDD.