Early Diagnosis and Screening of Autism Spectrum Disorders

Catherine Lord, PhD; Rhiannon Luyster


December 27, 2005

In This Article

Screening for ASD: Current Findings

The Checklist for Autism in Toddlers

Figure 1 lists the various screening tools used for identifying ASD. Population screening for ASD was initially attempted in the United Kingdom using the Checklist for Autism in Toddlers (CHAT),[1] which emphasized joint attention and imagination. Nurses visited 18-month-old children at home and administered the CHAT activities to them and a series of questions to their parents. Most children classified by the CHAT were later diagnosed with autism. However, upon follow-up, it became evident that the CHAT had missed more than three quarters of children who eventually received ASD diagnoses. Furthermore, children with suspected developmental disabilities had been eliminated even before the screening, so it was unclear how the overlap between autism and mental retardation would be treated.

Figure 1.

Levels of screening and diagnosis for children with ASD at age 2 years or younger.

Modified CHAT

In 2001, Robins and colleagues[2] published results of a study of a modified version of the CHAT, the M-CHAT, which they administered to children 24 months of age who were recruited from pediatric practices and special education programs in the United States. This modified version eliminated the nurse-administered component and added more parent questions. Like the CHAT, the M-CHAT identified children with autism at age 2 years, but because most of these children had been recruited from special education programs, a larger population-based study of the M-CHAT is necessary (and is underway).

The Early Screening for Autistic Traits

The Early Screening for Autistic Traits (ESAT),[3] puts a greater emphasis on play and less on joint attention than the previous instruments. Results of investigations of this tool indicated that children with high scores on the ESAT were likely to have developmental problems, but for children younger than 24 months, the measure did not differentiate well between ASD and non-ASD. Moreover, like the CHAT and M-CHAT, it also missed many children who later received ASD diagnoses.[3,4] Nevertheless, despite the ESAT's poor sensitivity, the study increased public awareness and provided a simple way to pursue referrals, and thus early identification increased.

The Communication Symbols Behavior Scales

The Communication Symbols Behavior Scales (CSBS)[5] is a 1-page parent questionnaire designed to identify communication disorders, rather than ASD in particular, in 6- to 24-month-old children. If children screen positive, a direct assessment (the Behavior Sample) and an additional parent-caregiver questionnaire are administered. The Scale of Red Flags (SORF)[6] for autism was developed for scoring the Behavior Sample as a level 2 screener. It successfully identified most children with language delay as having or not having autism.

The Social Communication Questionnaire

The Social Communication Questionnaire (SCQ)[7] is a parent-caregiver questionnaire intended to identify potential participants for autism studies. It was normed on older children and adults. Research by Corsello and colleagues (unpublished data, 2005) has indicated that if the cut-off is adjusted to require fewer endorsed items, the SCQ worked well for children as young as 3 years old.[8] However, the children studied had already been referred for services, so the appropriateness of the SCQ with the general population is unclear, as is its usefulness with children younger than 3 years old.


The Screening Test for Autism in Two Year Olds (STAT)[9] is directly administered to the child by a trained examiner. It discriminates well between children with ASD and children with other developmental disorders. It is intended for children already suspected of having ASD.

Two other well-known scales are the Gilliam Autism Rating Scale (GARS)[10,11] and the Childhood Autism Rating Scale (CARS).[12] Both of these tools are primarily intended for level 2 screening but they are sometimes mistakenly used as diagnostic instruments. Both instruments are not commonly used with young children.


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