Standards of diagnostic assessment for autism spectrum disorder (2024)

Abstract

The rising prevalence of autism spectrum disorder (ASD) has created a need to expand ASD diagnostic capacity by community-based paediatricians and other primary care providers. Although evidence suggests that some children can be definitively diagnosed by 2 years of age, many are not diagnosed until 4 to 5 years of age. Most clinical guidelines recommend multidisciplinary team involvement in the ASD diagnostic process. Although a maximal wait time of 3 to 6 months has been recommended by three recent ASD guidelines, the time from referral to a team-based ASD diagnostic evaluation commonly takes more than a year in many Canadian communities. More paediatric health care providers should be trained to diagnose less complex cases of ASD. This statement provides community-based paediatric clinicians with recommendations, tools, and resources to perform or assist in the diagnostic evaluation of ASD. It also offers guidance on referral for a comprehensive needs assessment both for treatment and intervention planning, using a flexible, multilevel approach.

Keywords: Autism spectrum disorder, Diagnostic evaluation, Intervention planning

WHO SHOULD CONDUCT THE ASD DIAGNOSTIC ASSESSMENT?

In most provinces and territories, only physicians or psychologists are licensed to diagnose autism spectrum disorder (ASD) (1). In some communities, appropriately trained nurse practitioners may also make this diagnosis. Emerging evidence suggests that a trained sole practitioner can diagnose less complex cases of ASD (1–4), yet most clinical guidance documents recommend a team-based approach, led by a primary care provider, paediatric specialist, or clinical child psychologist who is trained to diagnose ASD (1,3–15).

THREE APPROACHES TOWARD AN ASD DIAGNOSTIC EVALUATION

Children with suspected ASD are often first identified by a paediatrician, family physician, parent, or another caregiver, and can present with a wide range and severity of symptoms. A ‘one-size-fits-all’ multidisciplinary team diagnostic approach is inefficient, and contributes to long wait times (1,16). This statement proposes three ASD diagnostic approaches, the choice of which depends upon the paediatric care provider’s clinical experience and judgment, and the complexity of symptom presentation (8–15) and/or psychosocial history (Figure 1). Regardless of the approach taken, open communication, collaboration, and consent to share information among professionals may help to achieve diagnostic accuracy and avoid duplication of effort.

PURPOSE AND ESSENTIAL COMPONENTS OF AN ASD DIAGNOSTIC ASSESSMENT

There are no diagnostic biomarkers for ASD. This condition is diagnosed clinically, based on information gathered from a detailed history, physical examination, and the observation of specific characteristic behaviours. Most guideline documents have not offered a maximal acceptable wait time for diagnosis (8,11–15), although three reputable guidelines recommend a 3- to 6-month interval between referral and assessment (6,7,10). An expedited ASD diagnostic assessment, or a referral for one, facilitates earlier and potentially concurrent access to educational interventions and community-based services. The three key objectives of the ASD diagnostic assessment are to:

1. Provide a definitive (categorical) diagnosis of ASD. In ambiguous cases (e.g., milder presentation, under the age of 2), a provisional diagnosis can be made, but the child must be monitored carefully, and referred for further, in-depth evaluation. In many jurisdictions, specialized ASD interventions are not available to children with a provisional diagnosis.

2. Explore conditions or disorders that mimic ASD symptoms and identify co-morbidities.

3. Determine the child’s overall level of adaptive functioning, including specific strengths and challenges, and personal interests, to help with intervention planning.

A family-centred approach is essential in the ASD diagnostic process because a substantial amount of time and care is required to listen to and talk with parents and other family members. Understanding the child’s family and medical history, along with current behaviours and individual and family treatment goals, is central to family-centred care. This approach also requires flexible appointment scheduling and anticipating potential barriers to health care access (e.g., socio-economic adversity), as well as considering cultural and religious values (8–10). When families and clinicians do not speak the same language, involving interpretation services is essential for culturally competent care.

The essential elements of an ASD diagnostic assessment are described below.

STEP 1: RECORDS REVIEW

Most diagnosing clinicians begin by reviewing a child’s previous records and interviewing parents and caregivers about their concerns. This process is typically followed by taking a detailed developmental history and scheduling an appointment for direct observation and assessment.

STEP 2: INTERVIEWING PARENTS, FAMILY MEMBERS, OR OTHER CAREGIVERS

Information is obtained by asking semi-structured, open-ended questions, and may be integrated with information from a standardized questionnaire completed before or during the interview. Topics include:

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  Reasons for referral, and when concerns first emerged

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  Pregnancy, birth history, labour, with any delivery or other complications

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  Child’s developmental and behavioural history (refer to baby books and home videos, when available)

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  Child’s current developmental functioning and behaviours

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  Child’s medical history, with focus on ASD-associated difficulties, such as sleep problems, unusual diet, self-injury

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  Child’s early intervention and educational history, when available

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  Family medical and mental health history, spanning three generations, if possible. Inquire into any history of developmental disability, including ASD, learning difficulty, behavioural problems, as well as genetic conditions. Include psychosocial history, with focus on family violence or trauma, substance abuse, or neglect

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  Family functioning, strengths, routines, and resources. Consider possible reactions to an ASD diagnosis, along with individual and family goals

STEP 3: ASSESSMENT FOR CORE FEATURES OF ASD

This step involves observing and interacting with the child to assess social interaction and communication abilities. Inquire about or observe for patterns of behaviour or interests, with focus on DSM-5 diagnostic criteria for ASD (17). Behavioural observation in multiple settings is preferred (e.g., clinic, home, or child care), but most assessments occur in clinical settings. An ASD-specific diagnostic tool may also be used.

STEP 4: COMPREHENSIVE PHYSICAL EXAMINATION AND ADDITIONAL INVESTIGATIONS

The physical exam assesses whether there are medical causes or associations with the child’s behavioural presentation. Findings can help to guide treatment and intervention planning and include:

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  Height and weight

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  Head circumference (20% of individuals with ASD are macrocephalic)

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  Skin examination for signs of neurofibromatosis or tuberous sclerosis (e.g., using Wood’s lamp)

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  Neurological examination

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  Congenital anomalies and dysmorphic features (e.g., large or prominent ears)

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  Hearing and vision assessment with referral to audiologist, optometrist, or ophthalmologist, as needed

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  Only if clinically indicated, laboratory testing or further investigations may include:

  • Electroencephalogram (EEG) (e.g., for seizures)

  • Magnetic resonance imaging (MRI) (e.g., for microcephaly, seizures, abnormal neurological exam)

  • Metabolic testing (e.g., for cyclic vomiting, lethargy with minor illness, developmental regression, and seizures) (23)

  • Chromosomal microarray genetic testing should be offered for any children with a developmental disability, dysmorphic features, or congenital anomaly (24,25)

  • Blood lead levels, when the child exhibits developmental delay or pica, or lives in a high-risk environment

STEP 5: CONSIDER DIFFERENTIAL DIAGNOSES AND CO-OCCURRING CONDITIONS

When making an ASD diagnosis, it is important to consider other disorders that might overlap or mimic ASD symptoms. Table 2 summarizes common differential diagnoses that may also co-occur with ASD.

STEP 6: ESTABLISHING AN ASD DIAGNOSIS

A trained clinician uses DSM-5 criteria along with clinical judgment to differentiate ASD from other developmental disorders (1). For a description of DSM-5 criteria, see Table 1 on pg 425, Early Detection for Autism Spectrum Disorder, in the companion statement published in this issue.

STEP 7: COMMUNICATING ASD DIAGNOSTIC ASSESSMENT FINDINGS

Ideally, both parents and the child (when age and otherwise appropriate) should be invited for a face-to-face appointment shortly after the ASD diagnostic evaluation. This visit should be conducted in the family’s primary language, using an interpreter if necessary, with discussion of assessment findings, prognosis, and recommended supportive resources. When an in-person appointment is not possible due to remote location or travel restrictions, a telephone- or video-conference should be arranged instead.

This appointment must be handled in a sensitive, supportive manner. Parents should be given time to process the information being given and to ask questions, without distractions or interruptions. Asking parents what questions they have (rather than if they have questions) is one helpful way to open a conversation. When both parents are involved in the child’s care, they should be present together for the feedback meeting. A lone parent should be encouraged to bring a support person to this appointment.

The information below should be provided verbally and as part of a comprehensive, informative written report, with terms and references suitable for a lay audience.

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  A clear statement confirming that the child does (or does not) have ASD (e.g., ‘[Child’s name] meets DSM-5 criteria for a diagnosis of ASD’). Avoid indirect language (e.g., ‘[Child’s name’s] behaviour is consistent with a diagnosis of ASD’) because it can be confusing. In some cases, a provisional diagnosis may be appropriate, especially when targeted local services are available.

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  The reasons for the referral, and the child’s relevant developmental and family history.

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  Summary of pre-evaluation test results, and a review of all relevant records.

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  Summary from the family interview and direct observations of the child that support the ASD diagnosis.

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  Description of the diagnostic tools used, and clinicians who conducted the evaluation.

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  Description of how the child’s presenting symptoms, behaviours, and history meet DSM-5 criteria.

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  Co-occurring or suspected conditions that have been identified, diagnosed, or require further investigation.

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  Current functioning levels and recommended supports.

  • ◦ Referrals for services, with individualized intervention recommendations based on the child’s needs

  • ◦ Recommended additional assessments, when needed

  • ◦ Resources for parents (e.g., information about ASD, support and parent advocacy groups, funding opportunities) and siblings, and a follow-up plan.

STEP 8: COMPREHENSIVE ASSESSMENT FOR INTERVENTION PLANNING

After a child has been diagnosed with ASD, the paediatric clinician’s role is to ensure that a comprehensive needs assessment for treatment and intervention planning is considered, when this step was not part of initial diagnostic evaluation. This may involve advocating for further assessment if it appears that a lack of clarity about the child’s functioning may undermine effective planning. This assessment may recur or be revisited at different points throughout child or adolescent development, and in many cases will occur within the context of the child’s educational or treatment program. Understanding overall levels of functioning in several domains, including strengths, skills, challenges, and needs, helps with developing effective, individualized treatment and management planning. Such plans should also consider both individual and family concerns, priorities, and resources. The needs assessment may evaluate:

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  Cognitive and academic functioning

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  Speech, language, and communication skills

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  Sensory and motor functioning, and sensory sensitivities

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  Adaptive functioning (e.g., self-help skills)

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  Behavioural and emotional functioning (e.g., anxiety, self-esteem issues)

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  Physical health and nutrition

The extent of comprehensive assessment for intervention planning is influenced by the approach used for initial ASD diagnostic evaluation.

OTHER CONSIDERATIONS IN DIAGNOSTIC EVALUATION

NEXT STEPS FOLLOWING A CONFIRMED ASD DIAGNOSIS

When an ASD diagnosis has been confirmed, a community-based paediatrician or primary care provider plays a vital role in supporting both child and family. Physicians provide routine health care, manage co-occurring medical conditions, and coordinate care among medical, educational, community, and social care professionals. For additional information on condition management, read the companion statement published in this issue, including links to online resources.

Funding

Production of these guidelines has been made possible through funding from the Public Health Agency of Canada. The views expressed herein do not necessarily represent the view of the Public Health Agency of Canada.

Potential Conflicts of Interest

Dr. Zwaigenbaum reports personal fees from Roche - Independent Data Monitoring Committee (iDMC), outside the submitted work. There are no other disclosures. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

CANADIAN PAEDIATRIC SOCIETY AUTISM SPECTRUM DISORDER GUIDELINES TASK FORCE

Members: Mark Awuku MD (CPS Community Paediatrics Section), Jessica Brian PhD (co-Chair), Susan Cosgrove, Pam Green NP, Elizabeth Grier MD (College of Family Physicians of Canada), Sophia Hrycko MD (Canadian Academy of Child and Adolescent Psychiatry), Angie Ip MD, James Irvine MD, Anne Kawamura MD (CPS Developmental Paediatrics Section), Sheila Laredo MD PhD (Canadian Autism Spectrum Disorders Alliance), William Mahoney MD (CPS Mental Health Section), Patricia Parkin MD, Melanie Penner MD, Mandy Schwartz MD, Isabel Smith PhD, Lonnie Zwaigenbaum MD (co-Chair)Principal authors: Jessica A. Brian PhD, Lonnie Zwaigenbaum MD, Angie Ip MD

References