Making a Diagnosis of Autism Spectrum Disorder - A Closer Look

What are the key elements of your discussion with Billy’s mother?
  • When you are discussing your concerns with a family it is often helpful to give specific examples of your concerns (e.g., poor eye contact, lack of joint attention). It is also important to emphasize good skills the child is exhibiting (e.g., “Billy seems to be very attached to you. I’m glad to hear he has been making progress since he started therapy.”)
  • Explain the importance of further evaluation and arriving at a diagnosis. It is also important to acknowledge the parents’ worries. Many parents do not want their child to be “labeled” and may be hesitant to have a diagnosis given. Explain that having a specific diagnosis helps ensure their child will receive appropriate therapies and interventions.
  • It is important to refer the child for early intervention services as soon as ASD or other developmental disability is suspected. Educate the family on the importance and benefits of starting therapy as early as possible without creating undue panic or alarm.
  • Find out what the family knows about ASD. It is usually helpful to explain that ASD is a spectrum and that no two children will have exactly the same characteristics. Each child will have his or her own individual strengths and weaknesses and a child may need more support in some areas than others.
  • Give the family literature on ASD and direct them to resources available in the area.
  • Answer any questions the family may have and be available if they have questions in the future.
  • Emphasize that children with ASD do continue to have warm relationships. It is important for families to have a balance of reality and optimism.

See the Communicating Concerns: Screening and Diagnosis Results for more detailed information.

What are the usual components of a diagnostic evaluation for ASD?

  • Medical history – significant pre- and perinatal problems, medical issues, surgeries or hospitalizations, seizures, ear infections, results of newborn screen, prenatal history of alcohol exposure, rubella or CMV, results of hearing and vision screens
  • Developmental history – language, social, and motor milestones, history of any developmental regression; current communication abilities
  • Behavioral history – current behavior, socialization, odd or stereotypical behaviors, play interests
  • Family history – ASD, language disorders, intellectual disabilities, learning disabilities, ADHD, depression, schizophrenia, or other mental illnesses, obsessive-compulsive disorder, genetic disorders

A child and his mother at the doctor's office
  • General examination
  • Growth parameters including head circumference
  • Neurological exam
  • Skin examination
  • Look for dysmorphic features

Assessment of functioning across all developmental domains. Common tests in use (depending on child’s age and abilities) that may be performed by a variety of specialists on a multidisciplinary team include:

  • Cognitive
    • Bayley Scales of Infant Development
    • Mullen Scales of Early Learning
    • Wechsler Preschool and Primary Test of Intelligence
    • Wechsler Intelligence Scale for Children
    • Stanford-Binet Intelligence Scales
  • Speech and Communication
    • Preschool Language Scale
    • McArthur Communicative Development Inventory
  • Motor
    • Peabody Developmental Motor Scales
  • Adaptive
    • Vineland Adaptive Behavior Scales
    • Sensory Profile

Clinical expertise with review of the DSM-5 criteria must be used to interpret the results of the objective tests. Commonly used tools include the following:

  • Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) – The examiner observes the child through a series of structured and semi-structured scenarios, and rates the child based on his or her social interaction, communication, and stereotyped behaviors. The module to be administered is selected according to the child’s verbal ability.
  • Autism Diagnostic Interview-Revised (ADI-R) – This is a comprehensive, structured interview administered by a trained clinical interviewer to the parent or caregiver. It includes 92 questions about the child’s language and communication, social interaction, and behavior/interests.
    • The ADOS-2 and ADI-R both require extensive training and clinical expertise.
  • Other tools may include the Childhood Autism Rating Scale, Second Edition (CARS-2) and Gilliam Autism Rating Scale, Third Edition (GARS-3).
    • CARS-2 is a 15-item scale that assesses for clinical symptoms of autism. It is completed by the examiner based on obtained history and observation. Resulting scores are categorized as “no autism,” “mild to moderate autism,” or “severe autism.”
    • The GARS-3 assists teachers, parents, and clinicians in identifying autism in individuals and estimating its severity. It consists of 56 clearly stated items describing the characteristic behaviors of persons with autism.

What is the medical/genetic workup for a child with suspected ASD?

The approach to the genetic workup of a child with suspected or confirmed ASD has become increasingly complex as the diagnostic options available have rapidly evolved. With the introduction of newer technologies, the reported “yield” rates of genetic evaluations have increased, and are currently estimated to be about 15% (with some reports suggesting rates as high as 40%). Evaluations should always be customized, taking into account the clinical findings, family interest, cost, and practicality.

  • In the past, high-resolution karyotype and DNA testing for fragile X syndrome (fragile X) were the first-line tests to be performed when a diagnosis of ASD was made.
  • Some more recent guidelines recommend that a technology known as array comparative genomic hybridization (aCGH, may also be called microarray or chromosome microarray) should replace the karyotype as a first-line test. This test uses computer chip technology to screen multiple segments of DNA simultaneously, allowing for the detection of tiny microdeletions and microduplications in the genome (also known as copy number variants). Many of the currently available chips test for most of the known microdeletion syndromes, the subtelomeric regions, and other ASD “hot spots.”
  • Testing for genetic causes is often performed after the ASD diagnosis is made, but in some cases the testing may be performed during the initial ASD evaluation, particularly when co-occurring intellectual disability is present.

A little girl in a yellow shirt

Additional tests may be performed based on the clinical presentation. A selected few include:

  • MECP2 DNA sequencing for Rett syndrome in females with ASD, especially if they are microcephalic
  • PTEN gene testing for Bannayan-Riley-Ruvalcaba syndrome in children with ASDs and head circumference > 2.5 SD above mean
  • Genetic evaluation for tuberous sclerosis or neurofibromatosis in children with abnormal skin pigmentation (ash leaf or café au lait macules, respectively)
  • Fluorescence in situ hybridization (FISH) may be ordered when a specific diagnosis caused by a microdeletion syndrome (e.g., Angelman syndrome) is being considered

Finally, mitochondrial disorders and dysfunction as well as other metabolic disorders should be considered. One neurometabolic disorder that has an autistic phenotype is phenylketonuria (PKU).

What are the core features of ASD?

The diagnostic criteria for autism and related disorders have undergone many revisions since the term “infantile autism” first appeared in the DSM-III in 1980.

  • In 1994, the DSM was revised to include five diagnostic categories under the umbrella term “pervasive developmental disorders”: autistic disorder (AD), Asperger syndrome (AS), pervasive developmental disorder – not otherwise specified (PDD-NOS), Rett syndrome, and childhood disintegrative disorder.
  • In recent years, clinicians and researchers began referring to autistic disorder, Asperger syndrome, and PDD-NOS together as “Autism Spectrum Disorders” or “ASDs”.
  • The DSM-5, released in May, 2013, uses the term “Autism Spectrum Disorder” to refer to these conditions, and the criteria for making the diagnosis of autism spectrum disorder were adjusted. These criteria encompass clinical signs pertaining to the two primary areas of impairment seen in ASD.
    • While reviewing the criteria, it is important to keep in mind the wide heterogeneity of symptoms, severity, and clinical presentations that characterize children with ASD.
    • Individuals with an existing PDD diagnosis (including Asperger syndrome) are now considered to have ASD.

Impairments in Social Interactions and Communication(Social)

All children on the autism spectrum share an inherent difficulty in their ability to relate socially to, or connect with, others. Children with ASD may prefer to be alone, make poor eye contact, and have difficulty interpreting the facial expressions of others. They often don’t respond to bids for their attention, and conversely, may rarely attempt to gain the attention of another.

Deficits in joint attention are characteristic of children with ASD, as is a lack of “shared affect” (sharing one’s emotional state with another, e.g., through a smile) and “showing” behaviors (taking an object over to another in order to share their interest in it with them).

Although delayed speech is often the first concern to be raised by parents, it is not a primary diagnostic characteristic of ASD. Instead, if the social use of communication is lacking, it would be important to evaluate for ASD.

At any level of verbal language, the child usually has challenges in nonverbal or social use of language. For example, he or she may not use gestures or eye contact to regulate social interaction. Language may be atypical, and lacking in communicative intent.

Because of their difficulties with these basic building blocks of social behavior, children with ASD often have great trouble in forming relationships and making friends.

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A little boy who is upset about something.

Restricted and Repetitive Behavior, Interests, or Activities (RRBs)

Children with ASD often demonstrate a range of behaviors that are atypical, appear purposeless, and tend to be performed in a repetitive fashion. Motor stereotypes include behaviors such as hand flapping, unusual finger movements, rocking, and spinning. Language may be characterized by abnormal tone and prosody (pitch, intonation, stress, and rhythm used in speech “echolalia” (repeating or “echoing” words for phrases), or “scripting” (e.g., repeating lines from a favorite TV show). Play is often perservative in nature and may be limited to lining toys up or spinning or mouthing objects. Children with ASD may adhere to strict routines in their daily lives and will often have a tantrum when the routine is disrupted. They may develop preoccupations and attachments with atypical objects, such as a piece of paper or string. For some children, restricted interests are often manifested in their obsession with certain topics (e.g., dinosaurs or the solar system).

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Co-occurring conditions

Co-occurring conditions, while not part of the core features of ASD, may occur frequently in children with ASD. Some of these include:

  • Global developmental delay, intellectual disability, uneven cognitive abilities (sometimes referred to as splinter skills)
  • Atypical motor development, poor coordination, or deficits in praxis
  • Co-morbid symptomatology of other DSM-5 disorders, such as ADHD and anxiety disorders
  • Sleep problems
  • Gastrointestinal disorders
  • Seizure disorders

For more information on co-occurring conditions, see the Autism-Specific Anticipatory Guidance Module.

What are the DSM-5 criteria for ASD?

Persistent deficits in social communication and social interaction across multiple contexts, as manifested by the following, currently or by history:

  • Deficits in social-emotional reciprocity, ranging, for example, from abnormal social approach and failure of normal back- and- forth conversation; to reduced sharing of interests, emotions, or affect; to failure to initiate or respond to social interactions.
  • Deficits in nonverbal communicative behaviors used for social interaction, ranging, for example, from poorly integrated verbal and nonverbal communication; to abnormalities in eye contact and body language or deficits in understanding and use of gestures; to a total lack of facial expressions and nonverbal communication.
  • Deficits in developing, maintaining, and understanding relationships, ranging, for example, from difficulties adjusting behavior to suit various social contexts; to difficulties in sharing imaginative play or in making friends; to absences of interest in peers.

Category 2: Restricted, repetitive patterns of behavior, interests , or activities (RRBs)

Restricted, repetitive patterns of behavior, interests, or activities (RRBs) as manifested by at least 2 of 4 symptoms currently or by history.

  • Stereotyped or repetitive speech, motor movements, or use of objects, (e.g., echolalia, idiosyncratic phrases, simple motor stereotypies, lining up toys or flipping objects).
  • Insistence on sameness, inflexible adherence to routines, or ritualized patterns of verbal or nonverbal behavior (e.g. extreme distress at small changes, difficulties with transitions, rigid thinking patterns, greeting rituals, need to take same route or eat same food every day).
  • Highly restricted, fixated interests that are abnormal in intensity or focus (e.g., strong attachment to or preoccupation with unusual objects, excessively circumscribed or perservative interest).
  • Hyper- or hypo-reactivity to sensory input, or unusual interest in sensory aspects of the environment (e.g., apparent indifference to pain/temperature, adverse response to specific sounds or textures, excessive smelling or touching of objects, visual fascination with lights or movement)

  • At least five DSM-5 criteria must be met either by history or current behavior. 
    • All three criteria must be met from category 1, and
    • At least two criteria must be met from category 2.
  • In addition, symptoms:
    • Must be present in the early developmental period;
    • Must cause clinically significant impairment in social, occupational, or other important areas of current functioning; and
    • Must not be better explained by intellectual disability or global developmental delay.

Severity Ratings

New to the DSM-5 diagnostic criteria for ASD are severity ratings of the two symptom domains and the inclusion of clinical specifiers. 
 The severity ratings for the Social and RRB domains are based on the type and degree of impairments and level of support needed in these areas. 
Specifiers provide more clinically-relevant information about the child’s history and functioning; they include information about

  • Etiology,
  • Co-morbidities (e.g. intellectual disability, language delay, medical conditions such as seizures), and
  • Pattern of onset.