Disclaimer

There is no medical test for ASDs. Doctors look at behavioral symptoms to make a diagnosis. These symptoms may show up within the first few months of life or may appear at any time before the age of 3. 

In the past decade, research has found several behaviors that help to establish an early diagnosis of ASD. Also, research has shown that a diagnosis of autism at age 2 can be reliable, valid, and stable.^[1] But despite evidence that ASDs can often be identified at 18 months or younger, many children do not receive final diagnoses until they are much older. This delay results in lost opportunities for specialized early intervention. The earlier an ASD is diagnosed, the earlier needed interventions can begin.

CDC’s “Learn the Signs. Act Early.” campaign has interactive charts to help you keep track of your child’s development. 

General Developmental Screening and Surveillance
The diagnosis of an ASD takes two steps. The first step is developmental screening and surveillance during well-child doctor visits. Screening tests used solely for identifying children with developmental disabilities should be given to all children during the 9-month, 18-month, and 24- or 30-month well-child visits. If your child's health care professional does not routinely check your child with such a test, ask that it be done.

ASD-Specific Developmental Screening
Screening for ASDs is one way to improve early identification of children who need of more in-depth evaluation. Early intervention may be vital in preventing a cascade of problems that may affect later functioning. All children should be screened for ASDs at the 18-, 24-, and 30-month “well-child” visits. Additional screening may be needed if a child is at high risk for ASDs (has a sibling or parent with an ASD) or if symptoms warrant. See the  Screening Resources box for links to autism screening tools and their descriptions from the American Academy of Pediatrics (AAP).

Screening for High-Functioning Autism or Asperger Syndrome
Until recently, screening tools often did not identify children with mild ASD, such as those with high-functioning autism or Asperger syndrome. Today, the Autism Spectrum Screening Questionnaire (ASSQ), the Australian Scale for Asperger's Syndrome, and the Childhood Asperger Syndrome Test (CAST) are some of the tools that are reliable for identifying school-age children with Asperger syndrome or high-functioning autism. These tools focus on social and behavioral impairments in children without significant language delay.

If your child's doctor sees any of the possible signs of an ASD during a well-child visit, further evaluation is needed.

Comprehensive Diagnostic Evaluation
The second step of diagnosis is comprehensive evaluation. Thorough evaluation may include clinical observations, parent interviews, developmental histories, psychological testing, speech and language assessments, and possibly the use of one or more autism diagnostic scales. Because ASDs are complex disorders, a comprehensive evaluation may also include physical, neurological, and genetic testing.

Many tools have been designed to assess ASDs in young children, but no single tool should be used as the only basis for diagnosing autism. Diagnostic tools usually rely on two main sources of information—parents’ or caregivers’ descriptions of their child’s development and direct observation of behavior. 

Examples of autism diagnostic tools include:

• Autism Diagnosis Interview–Revised (ADI–R)[2]
• Autism Diagnostic Observation Schedule-Generic (ADOS–G)[3]
• Childhood Autism Rating Scale (CARS)[4]
• The Gilliam Autism Rating Scale (GARS)[5]

What can I do if I think my child has an ASD?
If you or your doctor thinks there could be a problem, ask for a referral to see a developmental pediatrician or other specialist. You can also call your local early intervention agency (for children under 3) or public school (for children 3 and older). To find out who to speak to in your area, check with the National Dissemination Center for Children with Disabilities.

Today, the main research-based treatment for ASDs is intensive structured teaching of skills, often called behavioral intervention. It is very important to start this intervention as early as possible to help your child reach his or her full potential. Acting early can make a real difference!  

Even if your child has not been diagnosed with an ASD, he or she may be eligible for early intervention services. The Individuals with Disabilities Education Act (IDEA) says that children under the age of 3 who are at risk of having substantial developmental delays may be eligible for services. These services are provided through an early intervention system in your state. Through this system, you can ask for an evaluation. To learn more about early intervention, click here National Dissemination Center for Children with Disabilities.

For tips on how to share your concerns with your pediatrician, visit the First Signs website.

Disclaimer: We have provided a link to these sites because they have information that may be of interest to you. CDC does not necessarily endorse the views or information presented on these sites. Furthermore, CDC does not endorse any commercial products or information that may be presented or advertised on these sites.

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Additional Information

Clinical Guideline: Screening and Diagnosis of Autism (American Academy of Neurology)

Clinical Guideline: The Pediatrician's Role in the Diagnosis and Management of Autistic Spectrum Disorder in Children (American Academy of Pediatrics)  

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