Position statement

Posted: Oct 24, 2019

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Lonnie Zwaigenbaum, Jessica A. Brian, Angie Ip; Canadian Paediatric Society, Autism Spectrum Disorder Guidelines Task Force

Paediatr Child Health 2019 24(7):424–432.

Autism spectrum disorder (ASD) is a life-long neurodevelopmental disorder, characterized by impairments in social communication, repetitive, restricted patterns of behaviour, and unusual sensory sensitivities or interests. ASD significantly impacts the lives of children and their families. Currently, the estimated prevalence of ASD is 1 in 66 Canadians aged 5 to 17 years. General paediatricians, family physicians, and other health care professionals are, therefore, seeing more children with ASD in their practices. The timely diagnosis of ASD, and referral for intensive behavioural and educational interventions at the earliest age possible, may lead to better long-term outcomes by capitalizing on the brain’s neuroplasticity at younger ages. This statement provides clear, comprehensive, evidence-informed recommendations and tools to help community paediatricians and other primary care providers monitor for the earliest signs of ASD—an important step toward an accurate diagnosis and comprehensive needs assessment for intervention planning.

Keywords: Autism spectrum disorder; Developmental surveillance; Early identification; Screening

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with onset in early childhood that is associated with a wide range of symptoms and ability levels. As defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) [1], ASD is an encompassing diagnostic category that includes two symptom domains: 1) social communication impairments, and 2) restricted, repetitive patterns of behaviours and interests. Other DSM-5 ASD diagnostic criteria are summarized in Table 1.

The prevalence of ASD has increased, from an estimated 1 in 1,000 children in Nova Scotia, an example cited 30 years ago [2], to a current estimate of 1 in 66 Canadians aged 5 to 17 years (1 in 42 males, and 1 in 165 females) [3]. The degree to which rising ASD prevalence is due to a true increase in cases is not yet known. Improved detection and diagnosis, and the broadening of diagnostic criteria with successive versions of the DSM, are likely contributors to changes in prevalence estimates [4]. Evidence suggests that ASD can be reliably diagnosed by 2 years of age in some children [5], though subtler cases may not present fully until later. Despite increasing awareness of early signs, the mean age of diagnosis remains 4 to 5 years of age [6]. While males are diagnosed with ASD four times more frequently than females [4][5], the sex gap may be narrowing. Recognition is growing that some girls present with more subtle signs than boys [7]–[9].

The etiology of ASD is not completely understood, though recent findings suggest an interplay among genetic, epigenetic, and environmental factors [10]. Strong risk factors for ASD include male sex and positive family history. Recurrence risk estimates for younger siblings of children with ASD range from 7% to 19% [11][12] versus 1.5% in the general population [4]. Recurrence varies by degree of familial relatedness. One recent Swedish study indicated a tenfold increase in relative risk when a full sibling has been diagnosed with ASD, as compared with a twofold increase when a cousin is affected [13]. Other risk factors are summarized in Table 2 [10]–[19]. The mechanisms associated with environmental exposure and ASD may include inflammation, oxidative stress, endocrine disruption and may be influenced by gene-related effects [15][16].

1. Impairment in social interaction and communication (all three subcriteria required)

Social and emotional reciprocity:

Impairment of nonverbal behaviours:

Failure to develop and maintain relationships:

2. Abnormal and restricted, repetitive behaviours, interests, and activities (two of four subcriteria required)

Stereotyped speech and behaviours:

Insistence on sameness/resistance to change:

Restricted, fixated interests:

Hyper- or hypo-sensitivity to sensory input

Overt behavioural signs of ASD are not generally present in the first 6 months of life. Prospective studies of high-risk infants suggest an emerging ASD prodrome in the latter half of the first year of life, which may include delayed motor control (e.g., persistent head lag), feeding and sleeping difficulties, and/or excessive reactivity or passivity [20][21].

Symptoms in the core domains of ASD usually emerge between 12 and 24 months. Initial presentations vary, and there is no one behavioural sign that rules an ASD diagnosis in or out. Parents’ initial concerns may include language delay, lack of response when the child’s name is said, and limited eye contact.

Other early warning signs at different stages of development are summarized in Table 3 [20]–[24]. Children with ASD may appear relatively typical with respect to early social engagement and communication, then become withdrawn or lose communication or language skills by 18 months [22]. For some children with more advanced language and cognitive skills, ASD signs are relatively subtle in the early years but become more apparent as they reach school age and begin to struggle with increasing social demands [20]–[23].

Developmental surveillance is a flexible process whereby knowledgeable clinicians gather relevant information over time from multiple sources (including parents and by direct observation) toward the goal of identifying and addressing developmental concerns, including those related to ASD [25]. The Canadian Paediatric Society (CPS) [26] and other professional organizations [27]–[38] recommend developmental surveillance at every scheduled health visit and any time a parent or caregiver raises concerns about a child’s language or other skills development. Developmental surveillance involves integrating information obtained from inquiry around parental concerns, clinical observations and, possibly, also incorporating standardized measures (e.g., parent questionnaires) to inform clinical impressions and decision making.

Developmental screening involves a brief assessment using a standardized measure to identify children at increased risk for delay or disorder. Screens vary by format (e.g., parent report versus direct assessment of the child) and scope (‘broadband’ screens cover multiple developmental domains versus those specific to a particular domain or disorder). Developmental screening also varies by target population. Universal screening targets all children regardless of level of concern, while targeted screening selects a subpopulation based on preidentified risk factors.

Genetic/familial

Specific genetic syndromes/risk variants

Male sex

First-degree relative or other family history of ASD

Prenatal

Older parental age (≥35 years)

Maternal obesity, diabetes, or hypertension

In utero exposure to valproate, pesticide, or traffic-related air pollution

Maternal infections (e.g., rubella)

Close spacing of pregnancies (