Diagnosis and evaluation of pervasive developmental disorders.

Accurate diagnosis and appropriate treatment of pervasive developmental disorders (PDDs), including autistic disorder, Asperger's disorder, and pervasive developmental disorder not otherwise specified, are necessary to ensure the best possible outcomes for children with these disorders. In the past, it was not uncommon for children with PDDs to wait several years from the time of parental recognition of developmental delay to the determination of the correct diagnosis and initiation of treatment. Increased awareness of PDDs and the availability of better assessment tools have improved the detection of these conditions in children. A wide variety of standardized diagnostic checklists, interviews, and observational measures are available to assist the clinician in making an accurate PDD diagnosis. A comprehensive evaluation also establishes a baseline of adaptive functioning and problematic behavior, which is essential for subsequent assessment of progress. This article discusses the differential diagnosis and evaluation of PDDs, focusing on the various assessment tools. The elements of a contemporary diagnostic evaluation and behavioral assessment are presented. The application of discretionary evaluations for special situations are also introduced.