INTRODUCTION
Screening and Diagnosis of Autism Spectrum Disorder
Developmental screening can be done by several professionals in health care, community, and school settings. However, primary health care providers are in a unique position to promote children’s developmental health.
Primary care providers have regular contact with children before they reach school age and can provide family-centered, comprehensive, coordinated care, including a more complete medical assessment when a screening indicates a child is at risk for a developmental problem.
Screening Recommendations
Research has found that ASD 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 they are much older. This delay means that children with ASD might not get the help they need. The earlier an ASD is diagnosed, the sooner treatment services can begin.
The American Academy of Pediatrics (AAP) recommends that all children be screened for developmental delays and disabilities during regular well-child doctor visits at:
- 9 months
- 18 months
- 30 months
Additional screening might be needed if a child is at high risk for developmental problems because of preterm birth or low birth weight.
In addition, all children should be screened specifically for ASD during regular well-child doctor visits at:
- 18 months
- 24 months
Additional screening might be needed if a child is at high risk for ASD (e.g., having a sibling with an ASD) or if symptoms are present.
It is important for doctors to screen all children for developmental delays, but especially to monitor those who are at a higher risk for developmental problems due to preterm birth, low birth weight, or having a sibling or parent with an ASD.
Health care providers diagnose ASD by evaluating a person’s behavior and development. ASD can usually be reliably diagnosed by age 2. It is important to seek an evaluation as soon as possible. The earlier ASD is diagnosed, the sooner treatments and services can begin.
Diagnosis in young children
Diagnosis in young children is often a two-stage process.
Stage 1: General developmental screening during well-child checkups
Every child should receive well-child check-ups with a pediatrician or an early childhood health care provider. The American Academy of Pediatrics recommends that all children receive screening for developmental delays at their 9-, 18-, and 24- or 30-month well-child visits, with specific autism screenings at their 18- and 24-month well-child visits. A child may receive additional screening if they have a higher likelihood of ASD or developmental problems. Children with a higher likelihood of ASD include those who have a family member with ASD, show some behaviors that are typical of ASD, have older parents, have certain genetic conditions, or who had a very low birth weight.
Considering caregivers’ experiences and concerns is an important part of the screening process for young children. The health care provider may ask questions about the child’s behaviors and evaluate those answers in combination with information from ASD screening tools and clinical observations of the child. Read more about screening instruments on the Centers for Disease Control and Prevention (CDC) website.
If a child shows developmental differences in behavior or functioning during this screening process, the health care provider may refer the child for additional evaluation.
Stage 2: Additional diagnostic evaluation
It is important to accurately detect and diagnose children with ASD as early as possible, as this will shed light on their unique strengths and challenges. Early detection also can help caregivers determine which services, educational programs, and behavioral therapies are most likely to be helpful for their child.
A team of health care providers who have experience diagnosing ASD will conduct the diagnostic evaluation. This team may include child neurologists, developmental pediatricians, speech-language pathologists, child psychologists and psychiatrists, educational specialists, and occupational therapists.
The diagnostic evaluation is likely to include:
- Medical and neurological examinations
- Assessment of the child’s cognitive abilities
- Assessment of the child’s language abilities
- Observation of the child’s behavior
- An in-depth conversation with the child’s caregivers about the child’s behavior and development
- Assessment of age-appropriate skills needed to complete daily activities independently, such as eating, dressing, and toileting
Because ASD is a complex disorder that sometimes occurs with other illnesses or learning disorders, the comprehensive evaluation may include:
- Blood tests
- Hearing test
The evaluation may lead to a formal diagnosis and recommendations for treatment.
Diagnosis in older children and adolescents
Caregivers and teachers are often the first to recognize ASD symptoms in older children and adolescents who attend school. The school’s special education team may perform an initial evaluation and then recommend that a child undergo additional evaluation with their primary health care provider or a health care provider who specialize in ASD.
A child’s caregivers may talk with these health care providers about their child’s social difficulties, including problems with subtle communication. For example, some children may have problems understanding tone of voice, facial expressions, or body language. Older children and adolescents may have trouble understanding figures of speech, humor, or sarcasm. They also may have trouble forming friendships with peers.
Diagnosis in adults
Diagnosing ASD in adults is often more difficult than diagnosing ASD in children. In adults, some ASD symptoms can overlap with symptoms of other mental health disorders, such as anxiety disorder or attention-deficit/hyperactivity disorder (ADHD).
Adults who notice signs of ASD should talk with a health care provider and ask for a referral for an ASD evaluation. Although evaluation for ASD in adults is still being refined, adults may be referred to a neuropsychologist, psychologist, or psychiatrist who has experience with ASD. The expert will ask about:
- Social interaction and communication challenges
- Sensory issues
- Repetitive behaviors
- Restricted interests
The evaluation also may include a conversation with caregivers or other family members to learn about the person’s early developmental history, which can help ensure an accurate diagnosis.
Receiving a correct diagnosis of ASD as an adult can help a person understand past challenges, identify personal strengths, and find the right kind of help. Studies are underway to determine the types of services and supports that are most helpful for improving the functioning and community integration of autistic transition-age youth and adults.
Developmental Screening Tools
Screening tools are designed to help identify children who might have developmental delays. Screening tools can be specific to a disorder (for example, autism) or an area (for example, cognitive development, language, or gross motor skills), or they may be general, encompassing multiple areas of concern. Some screening tools are used primarily in pediatric practices, while others are used by school systems or in other community settings.
Screening tools do not provide conclusive evidence of developmental delays and do not result in diagnoses. A positive screening result should be followed by a thorough assessment. Screening tools do not provide in-depth information about an area of development.
Selecting a Screening Tool
When selecting a developmental screening tool, take the following into consideration:
- Domain(s) the Screening Tool Covers
What are the questions that need to be answered?
What types of delays or conditions do you want to detect? - Psychometric Properties
These affect the overall ability of the test to do what it is meant to do.
- The sensitivity of a screening tool is the probability that it will correctly identify children who exhibit developmental delays or disorders.
- The specificity of a screening tool is the probability that it will correctly identify children who are developing normally.
- Characteristics of the Child
For example, age and presence of risk factors. - Setting in which the Screening Tool will be Administered
Will the tool be used in a physician’s office, daycare setting, or community setting? Screening can be performed by professionals, such as nurses or teachers, or by trained paraprofessionals.
Types of Screening Tools
There are many different developmental screening tools. CDC does not approve or endorse any specific tools for screening purposes. This list is not exhaustive, and other tests may be available.
Selected examples of screening tools for general development and ASD:
- Ages and Stages Questionnaire Third Edition (ASQ-3)
This is a general developmental screening tool. Parent-completed questionnaire; a series of 19 age-specific questionnaires screening communication, gross motor, fine motor, problem-solving, and personal adaptive skills; results in a pass/fail score for domains. Suitable for one month- 5 1/2 years old. - Communication and Symbolic Behavior Scales (CSBS)
Standardized tool for screening of communication and symbolic abilities up to the 24-month level; the Infant Toddler Checklist is a 1-page, parent-completed screening tool. - Parents’ Evaluation of Developmental Status-Revised (PEDS-R)
This is a general developmental screening tool. Parent-interview form; screens for developmental and behavioral problems needing further evaluation; single response form used for all ages; may be useful as a surveillance tool. - Modified Checklist for Autism in Toddlers (MCHAT)
Parent-completed questionnaire designed to identify children at risk for autism in the general population. - Screening Tool for Autism in Toddlers and Young Children (STAT)
This is an interactive screening tool designed for children when developmental concerns are suspected. It consists of 12 activities assessing play, communication, and imitation skills and takes 20 minutes to administer.
A more comprehensive list of developmental screening tools is available from the American Academy of Pediatrics (AAP), including descriptions of the tools, sensitivity, and specificity. The list includes general screening tools, as well as those for ASD.
Diagnostic Tools
There are many tools to assess ASD in young children, but no single tool should be used as the basis for diagnosis. Diagnostic tools usually rely on two main sources of information—parents’ or caregivers’ descriptions of their child’s development and a professional’s observation of the child’s behavior.
In some cases, the primary care provider might choose to refer the child and family to a specialist for further assessment and diagnosis. Such specialists include neurodevelopmental pediatricians, developmental-behavioral pediatricians, child neurologists, geneticists, and early intervention programs that provide assessment services.
Selected examples of diagnostic tools:
- Autism Diagnosis Interview – Revised (ADI-R)
A clinical diagnostic instrument for assessing autism in children and adults. The instrument focuses on behavior in three main areas: reciprocal social interaction, communication and language, and restricted and repetitive, stereotyped interests and behaviors. The ADI-R is appropriate for children and adults with mental ages of about 18 months and above. - Autism Diagnostic Observation Schedule- Second Edition– (ADOS-2)
A semi-structured, standardized assessment of social interaction, communication, play, and imaginative use of materials for individuals suspected of having ASD. The observational schedule consists of four 30-minute modules, each designed to be administered to different individuals according to their level of expressive language. - Childhood Autism Rating Scale- Second Edition (CARS-2)
Brief assessment suitable for use with any child over 2 years of age. CARS-2 includes items drawn from five prominent systems for diagnosing autism; each item covers a particular characteristic, ability, or behavior. - Gilliam Autism Rating Scale- Third Edition (GARS-3)
Assists teachers, parents, and clinicians in identifying and diagnosing autism in individuals ages 3 through 22. It also helps estimate the severity of the child’s disorder.
In addition to the tools above, the American Psychiatric Association’s Diagnostic and Statistical Manual, Fifth Edition (DSM-V) provides standardized criteria to help diagnose ASD.
From the National Institute of Mental Health
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