NEW YORK (Reuters Health) - Autism, a developmental disorder characterized by social withdrawal and an inability to communicate, is usually diagnosed during the pre-school years. But the disorder begins in infancy, and a group of British researchers have developed a behavior checklist that may help identify toddlers at risk for autism so they can get treatment earlier.

"There is some, although not uncontroversial, evidence of the benefits of early intervention programs,'' notes Dr. Tony Charman of the Institute of Child Health in London, and colleagues. "The possibility of early identification of autism merits investigation.''

The researchers developed a questionnaire called the Checklist for Autism in Toddlers, or CHAT, that can be used by parents and health care workers to identify toddlers who are at risk for developing autism, pervasive developmental disorder, and language disorders. The checklist focuses on behaviors that are usually missing in children with autism: interacting or playing with others, showing interest in things around them, and communication through language or pointing.

Of the more than 16,000 children screened with the CHAT at 18 months, 38 were considered at high risk for autism, and 369 at medium risk. The researchers looked at whether the screened children had autism or another developmental problems at ages 3 ½ years, 5 ½ years, and 7 to 8 years.

The team found that CHAT correctly identified 38% of the children who were later diagnosed with autism, and 32% of those later diagnosed with pervasive developmental disorder. Among the high-risk group, 27 of the 38 were not diagnosed with autism, but four of these developed language disorders and three had other developmental disorders.

The 38 high-risk children and half of the 369 medium-risk children were screened twice about one month after their first use of the CHAT. With these two screenings, the checklist's ability to predict later disorders went up: 83% of those identified as high risk were later diagnosed with either autism or pervasive developmental disorder. The researchers note, however, that this method of screening also missed number of children who did later develop these disorders.

Writing in the June issue of the Journal of the American Academy of Child and Adolescent Psychiatry, Charman and colleagues concluded that "the CHAT can be used to identify cases of autism and related pervasive developmental disorder at 18 months of age.'' They note, however, that the checklist is a screening tool only, and children identified through the screening tool require more detailed examination by experts.

"It is emphasized that the CHAT is not a diagnostic instrument but can identify potential cases of autism spectrum disorders for a full diagnostic assessment,'' the researchers stated. (SOURCE: Journal of the American Academy of Child and Adolescent Psychiatry 2000;39:694-702.)