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    ASD—How Is the Diagnosis Made?

    Updated at January 26th, 2023


    DisclaimerThis material is for educational purposes only. You, the reader, assume full responsibility for how you choose to use it. It is not intended to provide medical advice, diagnosis or treatment, nor does it replace the advice or counsel of a doctor or health care professional. Reference to a specific commercial product or service does not imply endorsement or recommendation of that product or service by CPCMG.

    Autism spectrum disorder (ASD) is complex, and symptoms are different for each child. Read on to learn more from the American Academy of Pediatrics about how ASD is diagnosed.

    Diagnosis of ASD can be complicated for a number of reasons. There are no specific medical tests (for example, a blood test) to diagnose ASD, so primary care doctors must rely on information from families about their child’s development and behavior and on what can be observed during well-child (also known as health supervision) checkups. This is why the AAP recommends that there be screening for ASD at specific well-child checkups (18- and 24-month visits) as well as ongoing surveillance in the course of well-child care. Talk with your child’s doctor if you feel your child needs to be screened, and share your concerns—you know your child the best.


    When ASD is suspected as a cause of language and social delays, the child should be referred for a comprehensive evaluation to determine whether ASD is the proper diagnosis and referred for Early Intervention (EI) services. The evaluation may be done by a doctor or psychologist who has expertise in the diagnosis of ASD or, preferably, by a team of specialists that might include developmental pediatricians, child neurologists, child psychiatrists, psychologists, speech-language pathologists, occupational or physical therapists, educators, and social workers.

    Testing of developmental abilities may occur through EI programs or the school system (depending on the child’s age).

    Typically, an evaluation will include

    • Careful observation of play and child-caregiver interactions.
    • Detailed history and physical examination.
    • Review of records of previous EI, school, or other evaluations.
    • Developmental assessment of all skills (motor, language, social, self-help, and cognitive). ASD is suspected when the child’s social and language functioning is significantly more impaired than his overall level of motor, adaptive, and cognitive skills.
    • Hearing test. All children with any speech delays or those suspected of having ASD should have their hearing formally tested.
    • Language evaluation that provides standardized scores of expressive language (including speech) and receptive language, as well as an evaluation of pragmatic language (social use of language) and articulation (pronunciation).

    Diagnosis of ASD is made by using all the information collected by history, observation, and testing.

    Medical Tests

    ASD may be associated with a known syndrome or medical condition. Newer, more sensitive tests have determined an underlying cause of ASD in many more children than was previously thought. Laboratory tests may be appropriate to rule out other possible medical conditions that could cause ASD symptoms depending on findings from the child’s history and physical examination. If they are appropriate, the child may be referred to another specialist, such as a geneticist or a pediatric neurologist, to help diagnose medical conditions that might cause or be associated with symptoms of ASD.

    Genetic Tests

    It is recommended that families be offered genetic testing, such as cytogenetic microarray testing, to help identify potential reasons a child might have autism. At present, up to 20% to 30% of children with ASD have abnormalities of their chromosomes that can be identified using cytogenetic microarray testing. Fragile X syndrome may be present in up to 2% of boys with ASD, so fragile X testing should also be considered. Testing girls with ASD symptoms for Rett syndrome may be discussed depending on findings from the child’s history and physical examination. Genetic testing should be strongly considered if a child has either unusual physical features or developmental delays or if there is a family history of fragile X syndrome, intellectual disability of an unknown cause, or other genetic disorders. Other genetic tests may be needed in certain cases. Recommendations for genetic testing may change as new tests are developed.


    Lead Test

    Lead screening is an important component of primary care. A test for lead level should be performed when a child lives in a high-risk environment, such as an older building, or continues to put things into his mouth.


    Other Tests

    Depending on findings from the child’s medical history and physical examination, other laboratory or imaging tests may be recommended but these are not required for all children with autism. Children with ASD may be picky eaters, so your child’s pediatrician may recommend looking for evidence of iron or vitamin deficiencies (especially vitamin D).


    NOTE: There is not enough clinical evidence to recommend any of the following tests specifically for ASD: hair analysis, routine measurement of multiple vitamin or nutrient levels, intestinal permeability studies, stool analysis, urinary peptide analysis, or measurement of mercury or other heavy metals.

    Visit HealthyChildren.org for more information.

    © 2019 American Academy of Pediatrics. All rights reserved.