How is autism spectrum disorder (ASD) diagnosed?

William Stillman
Health Education Specialist

Since the mid-1990s, autism has become more prevalent, its symptoms more widely recognized, and our physicians better educated about diagnosing it.

Remember, autism is a spectrum experience which can range from individuals who appear significantly impaired to those who have much milder symptoms.

Autism is diagnosed by ascertaining a collection of symptoms that may include little or no speech, lack of social engagement, challenges in fine- or gross-motor skills, and repetitive or perseverative actions, vocalizations, or activities. Any one of these traits in isolation does not make an individual autistic. For example, some children may experience developmental delays in muscle coordination or speech.

Where diagnosing autism can be challenging is if an individual has milder traits that go unnoticed, undetected or ignored (i.e., "They'll grow out of it."). When in doubt, raise any concerns with your pediatrician or general practitioner as early on in your child's development as possible so that he or she may be assessed. If diagnosed, your child may be eligible for an array of Early Intervention services and supports that will be designed to meet your family's needs.

A professional who has experience in evaluating children to determine whether they have autism spectrum disorder (ASD), such as a child psychologist, child psychiatrist, pediatric neurologist, developmental-behavioral pediatrician, or neurodevelopmental disabilities pediatrician, should evaluate the child. Generally, there should also be an evaluation of the intellectual function, speech-language, and hearing function, as well as a behavioral history and observation.

Joane Goodroe
Nursing Specialist

Research has shown that a diagnosis of autism at age 2 can be reliable, valid and stable. But many children with autism spectrum disorder do not receive final diagnoses until they are much older. Below is a link to a study that examined the age of diagnosis and how autism characteristics changed based on age.

Diagnosis of autism spectrum disorder (ASD) is tricky because it affects everyone differently, and there's no quick test to confirm it. Basically, if a person shows signs of ASD, a team of health professionals and experts will observe that person. They also ask the person's parents lots of questions to determine if he or she has ASD and how best to help him or her.

Dr. Latha Soorya, MD
Psychiatrist (Therapist)

There is no medical test for autism. An autism spectrum diagnosis is based on observed behavior and educational and psychological testing. There are several autism specific screening tools that can be used. Two autism specific screening tools that are used in toddlers include the M-Chat (Modified Checklist for Autism in Toddlers) and the PDDST (Pervasive Developmental Disorders Screening Test II- Stage 1). In older children and adults two autism specific screening tools are the SRS (Social Responsiveness Scale) and the SCQ (Social Communication Questionnaire). The gold standard research tools used to help make an autism spectrum disorder diagnosis are the ADOS (Autism Diagnostic Observation Schedule) and the ADI (Autism Diagnostic Inventory). These tools along with clinician judgment are used to make an autism diagnosis.

Dr. Ronald Leaf
Psychology Specialist

Watch me as I explain how autism is diagnosed.

At this time there is no medical test to diagnose autism. A diagnosis is made based on observed behavior, developmental history, and autism specific instruments when needed (ADOS, ADI). Therefore it is important for you to meet with clinicians who have expertise in this area.

Diagnosing Autistic Spectrum Disorders (ASDs) can be difficult since there is no medical test, like a blood test, to diagnose the disorders. Doctors look at the child’s behavior and development to make a diagnosis.

ASDs can sometimes be detected at 18 months or younger. By age 2, a diagnosis by an experienced professional can be considered very reliable. However, many children do not receive a final diagnosis until much older. This delay means that children with an ASD might not get the help they need.

Despite advances in understanding the neurobiology of autism spectrum disorder (ASD), we still must rely on behavioral manifestations of the condition to enable identification of children with ASD and to measure response to interventions. The evidence is well established that the earlier these children are identified and linked with treatment programs, the better their outcome.

Here is where primary care physicians enter the picture. Early symptoms of ASD can be subtle or confused with other developmental or physical dysfunction. The only reliable way to accomplish early diagnosis is through standardized screening for all children.

Reliable and efficient instruments are available, and their use is promoted by practice guidelines from organizations such as the American Academy of Pediatrics. The M-CHAT (Modified Checklist for Autism in Toddlers) is a brief parent-completed scale with clear scoring criteria that indicates risk for autism and need for further testing. It should be administered at 18 and/or 24 months of age.

Publicly funded programs such as BabyNet (for children up to age 3 years) or the Childfind program of your local school district (for children 3 years and older) can provide further screening and service coordination with links for diagnostic testing. The Autism Division of the Department of Disabilities and Special Needs (DDSN) also has service coordinators who can assist.

There are no shortcuts to diagnostic evaluation that relies on highly structured observations. Waiting lists are unavoidable, although much shorter than in the past.

Children at the higher functioning end of the autism spectrum might elude identification until older ages, when their social skills deficits become more evident (such as middle school). They still will benefit from an understanding of their atypical behavioral patterns and interventions to bolster their social skills.

The challenge faced by diagnosticians is to avoid over-labeling of behavior that is “quirky” but does not meet the diagnostic criteria for ASD and is not impeding successful functioning.

The contents of this website are for informational purposes only and are not intended to be a substitute for professional medical advice, diagnosis, or treatment. Nor does the contents of this website constitute the establishment of a physician patient or therapeutic relationship. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Autism spectrum disorder (ASD) varies widely in severity and symptoms and may go unrecognized, especially in mildly affected children, or when it is masked by more debilitating handicaps.

Many of the symptoms of autism spectrum disorders (ASDs) occur in very young children, so it is possible for children as young as 18 months to be diagnosed with ASDs. Early signs include delays in language and social development, as well as repetitive behaviors and poor eye contact.

Later indicators include:

  • Impaired ability to make friends with peers
  • Impaired ability to initiate or sustain a conversation with others
  • Absence or impairment of imaginative and social play
  • Stereotyped, repetitive or unusual use of language
  • Restricted patterns of interest that are abnormal in intensity or focus
  • Preoccupation with certain objects or subjects
  • Inflexible adherence to specific routines or rituals

Healthcare providers will often use a questionnaire or other screening instruments to gather information about a child's development and behavior. Some screening instruments rely solely on the parent's observations, while others rely on a combination of parent's and doctor's observations. If the screening instruments indicate the possibility of ASD, a more comprehensive evaluation is indicated.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.