How Is Autism Diagnosed in Children? What to Expect From an Autism Evaluation

Screening, evaluation, and diagnosis: what is the difference?

Families often hear these words used interchangeably. They are not the same.

For more on screening questionnaires such as the M-CHAT-R/F and on early signs by age, see our guide Early Signs of Autism in Toddlers.

Who can diagnose autism?

CDC lists neurodevelopmental pediatricians, developmental-behavioral pediatricians, child neurologists, geneticists, and early intervention programs that provide assessment services among the specialists a primary care provider might refer to. CDC's family-facing page adds that an evaluation may be done by one or more trained specialists, such as a developmental pediatrician, child psychologist, speech-language pathologist, or occupational therapist. [1] [2]

AAP's 2020 clinical report says most children will need to see a specialist, such as a developmental-behavioral or neurodevelopmental pediatrician, psychologist, neurologist, or psychiatrist, for a diagnostic evaluation. It also says general pediatricians and child psychologists who are comfortable applying DSM-5 criteria can make an initial clinical diagnosis, and that having a clinical diagnosis may help services begin. [3]

In practice, who does the evaluation depends on where you live, your insurance, and local wait lists. Some evaluations are done by a single clinician; others involve a team that meets together afterward.

What happens during an autism evaluation?

There is no single standard script. A U.S. survey of autism centers found wide variation in tools and in how long an evaluation takes (discussed below). [7] Still, the core ingredients described by CDC and AAP are consistent. [1] [2] [3]

1. A detailed developmental history

Expect many questions about your child's development from infancy onward: communication, play, relationships, routines, interests, sensory responses, sleep, eating, behavior, and medical and family history. AAP describes the history as reflecting a longitudinal picture of how symptoms affect a child's ability to function at home, with peers, and in school, gathered from caregivers, reports from other settings such as school or child care, and observations during testing. [3]

Some clinicians use questionnaires or a structured parent interview to organize this. AAP mentions the Social Communication Questionnaire (SCQ), the Social Responsiveness Scale (SRS), and the Autism Diagnostic Interview–Revised (ADI-R), a lengthy semistructured parent interview used in some clinical and research settings. AAP notes that none of these questionnaires is sufficient alone to make a diagnosis. [3]

2. Direct observation of your child

A clinician will play, talk, and interact with your child, often using toys and simple activities matched to your child's age and language. This is where structured observation tools may be used. AAP describes the ADOS-2 and CARS-2 as validated tools that provide structured data to support the diagnosis, and says no single observation tool is appropriate for all clinical settings. [3]

The ADOS-2 has modules for different ages, from toddlers to adults; AAP notes it takes about 30 to 45 minutes and requires intensive training to give and score accurately. The CARS-2 is a 15-item rating scale completed by the clinician from history and observation. [3]

These tools do not produce the diagnosis by themselves. AAP describes the critical element as a trained clinician integrating history and direct observation to decide whether the DSM-5 criteria are met. [3]

3. Testing of language, thinking, and daily living skills

AAP calls formal assessment of language, cognitive, and adaptive abilities and sensory status an important component of the diagnostic process. [3]

• Language: a speech-language pathologist can document understanding, expressive language, and the social use of language. [3] If language delay is part of the picture, our guide Speech Delay vs. Autism explains how clinicians think about the difference.
• Cognitive or developmental testing: helps clinicians tell whether social-communication differences are beyond what would be expected for a child's overall developmental level. AAP notes there are valid tests for children who do not speak. [3]
• Adaptive skills: caregiver or teacher reports of everyday skills, such as self-care and communication in daily life. AAP notes that documenting daily function can be needed for some publicly funded programs and helps set goals. [3]
• Motor skills: if screening suggests motor delays, AAP suggests formal evaluation by an occupational or physical therapist. [3]

4. Hearing and vision

AAP says children with language delay or inattention to language should have a hearing evaluation as part of the initial evaluation, and that vision should be considered in children who are visually inattentive, have certain repetitive visual behaviors, or do not make eye contact. [3]

5. Results, a report, and next steps

At the end, the clinician or team should explain whether your child meets criteria for autism, what other diagnoses were considered, and what your child's strengths and support needs are. CDC notes that the results of a formal evaluation highlight strengths and challenges and can show whether a child needs early intervention services. [1]

The evaluation may take one visit or several. Ask how long it will take, whether you will get results the same day, and when you will receive a written report.

If your child is diagnosed, the team will probably talk with you about supports and therapies. Choosing among them is a separate decision from the diagnosis itself. For one commonly recommended approach, our review Does ABA Therapy Work? What the Research Says for Autistic Children summarizes the evidence and its limits.

What are clinicians deciding? The DSM-5 criteria in plain language

The DSM-5 criteria, as reproduced by CDC, require persistent differences in social communication and social interaction across settings (all three areas: back-and-forth social connection, nonverbal communication such as gestures and eye contact, and developing and understanding relationships) plus at least two of four types of restricted or repetitive behaviors, interests, or activities. One of those four types is unusual responses to sensory input. [2]

The criteria also require that symptoms be present in the early developmental period, although they may not become fully apparent until social demands increase. AAP notes the symptoms must impair functioning. CDC's reproduction also states that the differences must not be better explained by intellectual disability or global developmental delay, which is why cognitive testing matters. [2] [3]

Two points help families read a report:

• Examples are not a checklist. The DSM-5 examples are illustrative, not exhaustive. A child does not need to show any particular behavior, such as lining up toys or avoiding eye contact, to be autistic, and showing one of them does not make a child autistic. [2]
• Severity levels describe support needs, not a score. DSM-5 describes three levels, from "requiring support" (Level 1) to "requiring very substantial support" (Level 3). AAP notes that the severity rating is not a quantifiable score that can be used to track progress. [2] [3] Reports may also note specifiers, such as whether there is accompanying intellectual or language impairment. [2]

If sensory differences are a big part of your child's day, see Sensory Differences in Autistic Children.

Are blood tests, brain scans, or genetic tests part of diagnosis?

Medical tests do not diagnose autism, but some can help answer other important questions. Here is what AAP's 2020 report recommends: [3]

• Genetic testing should be recommended and offered to all families as part of looking for an underlying cause. The usual first steps are chromosomal microarray (CMA) and fragile X testing, with further testing such as exome sequencing in some cases. In clinical samples, CMA found a clearly disease-causing change in a median of about 9% of autistic individuals (range 5.4% to 14%). AAP notes that a genetic diagnosis can inform counseling about prognosis and recurrence risk, help identify related medical conditions, and avoid unnecessary tests. Many children will not have a specific genetic cause identified. [3]
• Brain imaging (MRI) is not routine. AAP says it may be indicated for specific reasons, such as unusual regression, seizures, an abnormal neurologic exam, or unusual head size. [3]
• EEG is not recommended as a routine baseline test unless there is concern about seizures, atypical regression, or other neurologic symptoms. [3]
• Metabolic testing is not recommended for routine use, but may be guided by history and examination. AAP says there is no evidence for routine testing of hair, blood, or urine for environmental toxins or heavy metals, apart from standard lead screening. [3]

Be cautious about any service that offers a blood, hair, or stool "autism test." That is not how autism is diagnosed.

How reliable is a diagnosis in a toddler?

Generally reliable, with an important caveat. CDC says autism can sometimes be detected at 18 months or younger and that, by age 2, a diagnosis by an experienced professional can be considered reliable. AAP reports that most children (80% or more) diagnosed after a comprehensive evaluation before age 3 keep the diagnosis. [1] [3]

The clearest prospective data come from the Baby Siblings Research Consortium. Ozonoff and colleagues followed 418 younger siblings of autistic children at seven sites, with clinical diagnoses at 18, 24, and 36 months. Among children diagnosed at 18 months, 93% were still diagnosed at 36 months; at 24 months, 82%. But 41% of children who were autistic at 36 months had not yet been diagnosed at 24 months. [4]

What this means and does not mean:

• A diagnosis made by experienced clinicians at age 2 is usually confirmed later. [4]
• A "not autistic right now" result at 18 or 24 months is not always the final word, especially if differences are subtle. The authors concluded that longitudinal follow-up is critical for children with early signs of social-communication difficulties, even if they do not meet criteria at first. [4]
• These children had an older autistic sibling, so their results may not apply exactly to every child, and the authors note possible enrollment bias. They also suggest that screening may need to be repeated in the first years of life. [4]

AAP also notes that milder signs can be harder to recognize before age 3, especially in children with average or above-average cognitive abilities, and that a young child's long-term trajectory usually cannot be predicted at the time of diagnosis. [3]

Why does it take so long to get an autism diagnosis?

If you are on a waiting list, you are not imagining the problem.

• National surveillance: In CDC's 2022 surveillance data from 16 U.S. sites, published in 2025, the median age of earliest known autism diagnosis among 8-year-olds with a diagnostic statement was 47 months, ranging from 36 to 69.5 months across sites. These sites are not nationally representative. [5]
• Screening to diagnosis: A study of electronic health records from a large U.S. research network, mostly large academic medical centers, found an average delay of about 27 months from a child's first documented developmental screening to autism diagnosis among 1,915 autistic children. The data did not show which screening tool was used, whether the screen was positive, or whether a referral was made, so this cannot tell us where the delay happened. [6]
• Evaluation centers: A survey of U.S. autism evaluation centers reported initial waits ranging from under 4 weeks to more than a year and evaluations ranging from 1–2 hours to more than 8 hours, with a majority reporting waits longer than 4 months. Centers cited workforce shortages, referral volume, and documentation requirements. This was a poster report with an 11.1% response rate, and its authors included employees of a company that makes an autism diagnostic device, so treat the exact figures cautiously. [7]

CDC's surveillance report also found that testing practices varied widely between communities. [5] In other words, how a diagnosis is made, and how long it takes, can depend a lot on where you live.

Can an autism evaluation be done by telehealth?

Sometimes, yes. A 2023 systematic review of 18 studies, covering 1,593 children, found that telehealth diagnostic decisions agreed with in-person assessments in 80% to 88.2% of cases. The authors caution that many studies were small pilot or feasibility studies, many were rated low or moderate quality, most were done in high-income Western countries, and nearly 1 in 5 telehealth diagnoses was missed or incorrect. [8]

A 2025 study tested an in-home telehealth tool, the TELE-ASD-PEDS, with 182 children aged 18 to 42 months, recruiting with a focus on families who may face barriers to in-person evaluation. Every child had a telehealth assessment first. About two weeks later, half were randomly assigned to an in-person evaluation, and in that group the telehealth and in-person results (autism or not autism) matched in 94% of cases. Most children in the study (77%) were diagnosed with autism, and these are interim results from an ongoing trial. Four authors co-developed the tool; they report receiving no compensation for its use. [9]

Telehealth may shorten the path for some families, particularly young children with clearer presentations. A child with subtle signs, medical complexity, or a puzzling picture may still need an in-person assessment. [8]

A medical diagnosis and a school or early intervention evaluation are not the same

This confuses many families, and it matters.

• A medical or clinical diagnosis is made by a clinician using DSM-5 criteria. AAP notes that a clinical diagnosis may help services begin, and CDC's surveillance report notes that eligibility for some services can depend on specific documentation or testing. [2] [3] [5]
• An educational eligibility decision under the federal special education law (IDEA) is made by the school team. IDEA's definition of autism focuses on a developmental disability that significantly affects communication and social interaction and adversely affects a child's educational performance, and a child must also need special education to qualify. [10]

A child can have one without the other. In CDC's surveillance data, about two-thirds of autistic 8-year-olds had a documented autism special education eligibility and a similar share had a documented diagnostic statement, but these did not always overlap. [5]

You do not need to choose. If your child is under 3, you can contact your state's early intervention program and ask for an evaluation; if your child is 3 or older, you can contact your local school district. In the U.S., a medical diagnosis is not required first. Our guide How to Get Early Intervention Services explains the steps, timelines, and costs.

What you can do now

1. Speak up if you are worried. CDC says screening should happen whenever you or your doctor have a concern, not only at scheduled visits, and that you can ask for it. If screening or your concerns point to a closer look, ask about a referral for a diagnostic evaluation. [1]
2. Start early intervention or school services in parallel. Do not wait for a diagnostic appointment to request a developmental evaluation and support. See How to Get Early Intervention Services.
3. Get on more than one list if you can. Waits vary widely. Ask your insurer or pediatrician which evaluators are in network, and ask about cancellation lists or telehealth options. These are practical suggestions, not research findings.
4. Bring your observations. Short notes about what you see at home, examples from child care or school, and, if helpful, a brief video of an ordinary moment can help the clinician understand your child's everyday life. This is practical advice, not a test.
5. Ask about hearing. If speech or response to sound is part of the concern, ask whether a hearing test has been done. [3]
6. Keep communication supports going. Whatever the evaluation finds, a child who needs ways to communicate should have them now. See Does AAC Delay Speech?.
7. Know when to act quickly. If your child loses words, skills, or social engagement they used to have, contact the pediatrician promptly rather than waiting for the evaluation date. AAP notes that medical evaluation is indicated when a child loses milestones. [3]

Frequently asked questions

The bottom line

Autism is diagnosed through careful listening and watching, not a lab test. A good evaluation combines your knowledge of your child with direct observation and testing of language, thinking, and daily skills, and it checks hearing and other possible explanations. Diagnoses made by experienced clinicians in toddlers are usually stable, though some children are recognized later. Waits are common and practices vary, so it helps to start early intervention or school support in parallel and to keep asking questions until you have a plan. [1] [2] [3] [4] [5] [6] [10]