Diagnosing Autism

Since there is no blood test to determine the presence of autism, diagnosing this disorder can be difficult.  Doctors look at the child’s behavior and development to make a diagnosis.  Educators look at the impact these factors have on the student’s ability to access the general curriculum.  It is important to keep in mind that a medical diagnosis of autism and an educational diagnosis are not the same.

Medical Diagnosis

Autism Spectrum Disorder (ASD) can sometimes be detected at 18 months or younger.  By age 2, a diagnosis by an experienced professional can usually be considered reliable. However, many children do not receive a diagnosis until much older.  This delay means that children with ASD might not get the early intervention they need.

What does screening mean – does this mean there is a diagnosis?

Screening is a way to monitor development--it is not the same as a diagnosis. The purpose of screening is to identify children who might have a developmental delay or disorder.  Screening tools are developed for a specific problem or condition. Identifying atypical or delayed development as early as possible is important so that children can access appropriate interventions.  The American Academy of Pediatrics recommends screening for autism at both the 18-month and 24-month well-child visits.

What does Autism screening look like?

The screening process usually involves completion of a questionnaire by caregivers to assess social and communication development. It may also include direct observation by a specialist and a review of the child’s clinical history.  A variety of validated screening tools can be found here.

A good screening process will identify almost all of the children who have a delay or disorder. It will also, inevitably, identify some children who do not have the condition because no screening tool is perfect. The sensitivity of an autism screening tool indicates how well the tool correctly identifies children who have ASD and is the most important factor in a good screening tool.  If a physician suspects autism spectrum disorder, a referral should be made for a comprehensive evaluation. An audiology evaluation may also be ordered and often the child will be referred to Early Intervention (Part C) services.

Assessment & Diagnosis

An accurate diagnosis is based on a comprehensive history of early development and the observation or report of specific behavioral characteristics across a variety of environments and situations. The diagnostic criteria for autism are found in the Diagnostic and Statistical Manual – Fifth Edition (DSM-5) which can be viewed on the Autism Speaks website.

multidisciplinary diagnostic assessment  is recommended. This is a thorough review that differentiates autism from other developmental disabilities. The process should include direct observation with validated tools, and consideration of clinical history and caregiver concerns.   Additional assessment may include: review of medical history, neurological evaluation, genetic testing, metabolic testing, hearing and vision screening and other medical testing.

The assessment team should include professionals who have experience with assessing and diagnosing autism as well as the parents or primary caregivers for the child.  These professionals may include the following: pediatric neurologist, developmental pediatrician, child psychiatrist or psychologist or another licensed medical professional.  Given the impact autism has on social interaction, communication and other behaviors, it is also helpful to have a speech language pathologist, occupational therapist and behavior analyst on the team.  

Educational Diagnosis/Identification

A child who receives a medical diagnosis of Autism Spectrum Disorder will not automatically receive the educational disability category of Autism and may not immediately be eligible for special education services through the public school system. Parents are encouraged to contact the Special Education Department of their local school division to request an assessment when there is any concern that their child may have autism   Please visit the Virginia Department of Education’s (VDOE) website for more information. 


American Academy of Pediatrics, Council on Children With Disabilities, Section on Developmental and Behavioral Pediatrics, Bright Futures Steering Committee, Medical Home Initiatives for Children With Special Needs Project Advisory Committee. Identifying infants and young children with developmental disorders in the medical home: an algorithm for developmental surveillance and screening [published correction appears in Pediatrics. 2006;119:1808–1809]. Pediatrics. 2006;118 :405 –420
Gupta VB, Hyman SL, Johnson CP, et al. Identifying children with autism early [published correction appears in Pediatrics. 2007;119:867] Pediatrics. 2007;119 :152 –153