Updated March 05, 2015.

Although most pediatricians care for children with autism spectrum disorders, until recently few reported that they routinely screened for autism.

It is hoped that more pediatricians are routinely screening children for autism since the American Academy of Pediatrics (AAP) clinical report "Identification and Evaluation of Children With Autism Spectrum Disorders" came out in 2007. The report recommended that pediatricians:

• conduct surveillance for autism at every well-child visit, including looking for subtle signs
• screen children for autism using a formal screening tool or checklist when they are 18 and 24 months old
• schedule a special visit to address any concerns a parent may have about autism

Most important, the AAP recommends that pediatricians send children for a comprehensive autism evaluation if they have a positive autism screening test, in addition to signing them up for a hearing test and early childhood intervention services.

Autism Checklists for Toddlers

When people talk about tests for autism, they are usually referring to an autism checklist that can be used to screen toddlers, and not any kind of blood test.
Common checklists include the:

• Checklist for Autism in Toddlers (CHAT)
• CHAT, Denver Modifications
• Checklist for Autism in Toddlers-23 (has only been tested in China though)
• Modified Checklist for Autism in Toddlers, Revised with Follow Up (M-CHAT-R)
• PDD Screening Test-II, Primary Care Screener

All of these level 1 autism checklists can be filled out, typically by the parent, although some have questions that are answered by the pediatrician, in just five to 15 minutes.

One of these autism checklists should be used for all children in a family, even those who seem to be developing normally.

Level 2 autism screening checklists, usually used for toddlers who have a positive autism checklist, are also available. They can take from five to 20 minutes to complete, but require extra training to administer and interpret, so usually won't be available in your pediatrician's office. They include the:

• Autism Behavior Checklist (ABC)
• Childhood Autism Rating Scale (CARS)
• Gilliam Asperger's Disorder Scale (GADS)
• Gilliam Autism Rating Scale-2nd Edition (GARS-2)
• PDD Screening Test-II, Developmental Clinic Screener
• PDD Screening Test-II, Autism Clinic Severity Screener
• Screening Tool for Autism in 2-Year-Olds (STAT)

Modified Checklist for Autism in Toddlers

M-CHAT is one of the most popular autism checklists used by pediatricians. In addition to being quick and easy to use, it is available for free.

In fact, parents can even take the M-CHAT-R online and bring the results to their pediatrician.

A child has a positive screening for autism if three or more of the 20 total M-CHAT questions get a failed response.

An M-CHAT Follow-up Interview should also be done for children who have a positive M-CHAT screen. This follow up interview can help to decrease the number of children who fail the M-CHAT but who do not actually have autism - false positive test results. Children with a total M-CHAT score of 8 or  more probably don't need to have the M-CHAT-R Follow-up Interview and can go straight to the comprehensive autism evaluation.

Keep in mind that a positive M-CHAT screen doesn't always mean that a child has autism. Other causes of developmental delays could cause a positive screen too. That's why the next step should usually include a comprehensive autism evaluation, which would usually include level 2 autism screening, in addition to signing them up for a hearing test and early childhood intervention services.
 
<sub>Sources:

American Academy of Pediatrics Clinical Report. Identification and Evaluation of Children With Autism Spectrum Disorders. Pediatrics 2007 120: 1183-1215.

Kleinman JM. The modified checklist for autism in toddlers: a follow-up study investigating the early detection of autism spectrum disorders. J Autism Dev Disord. 01-MAY-2008; 38(5): 827-39</sub>