that has good discriminative validity between autistic spectrum and other disorders, including nonautistic mild or moderate mental retardation, in children age 4 years and older; it has not yet been tested with very young children. A score of 1 is given for an item if the abnormal behavior is present and a score of 0 if the behavior is absent. The cutoff for consideration of a diagnosis of autism is a score of 15 or higher. Further reliability studies and validation studies in younger children are ongoing. The recently published Screening Test for Autism in Two-Year Olds (Stone et al., 2000) is a direct observational scale; it showed good discrimination between children with autism and other developmental disorders in a small sample of two-year-old children.
Several additional instruments are currently undergoing validation studies. The Australian Scale for Asperger’s Syndrome (Garnett and Attwood, 1998) is a parent or teacher rating scale for high-functioning older children on the autistic spectrum who remain undetected at schoolage. The Pervasive Developmental Disorders Screening Test-II (PDDST-II) is a clinically derived parent questionnaire designed in three formats: Stage 1 is aimed for use in the primary care setting, Stage 2 for use in developmental clinics, and Stage 3 for use in autism clinics. The Modified Checklist for Autism in Toddlers (M-CHAT) expands the CHAT into a 23-item checklist that a parent can fill out in about 10 minutes (Robins et al., 1999). Other approaches are being developed.
Developmentally based assessments of cognitive, communicative, and other skills provide information important for both diagnosis and program planning for children with autism and related conditions. Careful documentation of a child’s unique strengths and weaknesses can have a major impact on the design of effective intervention programs and is particularly critical, because unusual developmental profiles are common. Given the multiple areas of difficulty, the efforts of professionals from various disciplines are often needed (e.g., psychology, speech and language pathology, neurology, pediatrics, psychiatry, audiology, physical and occupational therapy). The level of expertise required for effective diagnosis and assessment may require the services of individuals, or a team of individuals, other than those usually available in a school setting (Sparrow, 1997). In some cases, psychological and communication assessments can be performed by existing school staff, depending on their training and competence in working with children with autism. However, other services (e.g., genetic testing, drug therapy, management of seizures) are necessarily managed in the health care sector. Some children may fall between systems and therefore not be served well.
Several principles underlie assessment of a young child with autism