Diagnosing an Autism Spectrum Disorder (ASD) is often a two-stage process. The first stage involves general developmental screening during regular well-child checkups with a pediatrician. Children who show some developmental problems during a checkup are referred for additional evaluation. The second stage involves a thorough evaluation by a team of doctors with a wide range of specialties. After further evaluation, a child may be diagnosed as having ASD or another developmental disorder.

Children with ASD can typically be diagnosed by age 2, though recent research suggests that some screening tests can be helpful at as early as 18 months or younger. Many people—including pediatricians, teachers, and parents—may minimize signs of ASD at first, believing that children will “catch up” with their peers. While you may be concerned about labeling your child with ASD, the earlier the disorder is diagnosed, the sooner specific interventions may begin. Early intervention can reduce or prevent the more severe disabilities associated with ASD. Early intervention may also improve your child’s IQ, language, and everyday functional skills.


As recommended by the American Academy of Pediatrics, a regular well-child checkup should include a developmental screening test, with specific ASD screening at 18 and 24 months. Screening for ASD is not the same as diagnosing ASD. Screening instruments are used as a first step to determine whether a child needs more testing. If your pediatrician does not routinely screen your child for ASD, please insist that it be done.

Types of ASD screening instruments

Often the pediatrician will ask parents questions about the child’s symptoms to determine screening for ASD. Other screening instruments combine information from parents with the doctor’s own observations of the child. Examples of screening instruments include:

  • Checklist of Autism in Toddlers (CHAT)
  • Modified Checklist for Autism in Toddlers (M-CHAT)
  • Screening Tool for Autism in Two-Year-Olds (STAT)
  • Social Communication Questionnaire (SCQ)
  • Communication and Symbolic Behavior Scales (CSBS).

To screen for mild ASD in older children, the doctor may rely on different screening instruments, such as:

  • Autism Spectrum Screening Questionnaire (ASSQ)
  • Australian Scale for Asperger’s Syndrome (ASAS)
  • Childhood Asperger Syndrome Test (CAST).

Comprehensive diagnostic evaluation

The second stage of diagnosis must be thorough in order to find whether other conditions may be causing your child’s symptoms.

A team that includes a psychologist, a neurologist, a psychiatrist, a speech therapist, or other professionals experienced in diagnosing ASD may do this evaluation. The evaluation may assess the child’s thinking skills, language level, and adaptive behavior (age-appropriate skills needed to complete daily activities independently, such as eating and dressing).

Because ASD is a complex disorder that sometimes coexists with other syndromes or learning disorders, the comprehensive evaluation may include brain imaging and gene tests, along with in-depth memory, problem solving, and language testing. Children with any delayed development should also get a hearing test as part of the comprehensive evaluation.

Although children can lose their hearing along with developing ASD, common ASD symptoms (such as not turning to face a person while calling their name) can also make it seem that children cannot hear when in fact they can. If a child is not responding to speech, especially to his or her name, it’s important for the doctor to test whether a child has hearing loss.

The evaluation process is a good time for parents and caregivers to ask questions and get advice from the entire evaluation team. The outcome of the evaluation will assist in devising a plan for treatment and interventions to help your child.