Autism spectrum disorder (ASD), a common neurodevelopmental disability, typically can be diagnosed within the first 3 years of life, usually by age 24months. Themedian age of diagnosis in the United States is 4.5 years, which is substantially later than when symptomsemerge.
Despite increasing public awareness, only 43% of children with ASD receive a comprehensive developmental evaluation
by age 3 years.1 Timely detection facilitates access to appropriate developmental and behavioral intervention that, when begun soon after symptom onset, can substantially improve outcomes and reduce parents’ stress.
Autism spectrum disorder involves core impairments in social communication and the presence of stereotypic, restricted, and repetitive behaviors.One in 59 children (1.7%) in the United States had ASD in 2014, a 2.5-fold increase from the rate in 2000.
At least in part, this increase reflects better detection, including diagnosis of children with higher IQs, those with milder ASD symptoms, and members of racial/ethnic minority groups, who may have been previously overlooked or given other diagnoses. Prevalence rates also vary by US state and the ascertainment method used to estimate prevalence. There is marked heterogeneity in ASD presentation, with some individuals exhibiting prominent repetitive motor behaviors while others may have intense interests. Some individuals with ASD are minimally verbal, while others speak fluently but with
poor communication skills; intellectual functioning can be impaired or far greater than the mean. In addition, ASD has a strong genetic basis, with between 60% and 90% of the heterogeneity in symptom expression attributable to geneticvariation, reflecting both common allelic variants and structural variation in coding and noncoding regions of DNA. Younger siblings of children diagnosed with ASD (siblings at high risk) have an approximately 12-fold increased risk for ASD. Brain imaging studies demonstrate subtle alterations in white matter development, functional connectivity, and cortical growth prior to the emergence of core ASD symptoms in siblings at high risk who are subsequently diagnosed with ASD.
The American Academy of Pediatrics recommends ASD screening at ages 18 and 24 months using freely available online tools for clinicians and parents (https://m-chat.org/).
Parental concerns about infants’ behaviors, such as little or no babbling, poor eye contact, not pointing or sharing interests, few or no social smiles, reduced engagement, or not responding to voices or their name,may be the first indication of problems. Early prodromal signs of ASD unfold over the first year of life in siblings at high risk, although whether these very early developmental manifestations generalize to clinically ascertained ASD populations is less well established. In the first 6 months of life, there may be subtle sensory motor differences, with social communication deficits beginning to emerge later in the first year. Beginning early in the second year of life, restricted and repetitive behaviors may emerge. Individual differences are observed in the timing of ASD symptom onset, but by 24 months, most affected individuals can be diagnosed clinically . A small number of siblings at high risk exhibit slower symptom emergence, suggesting the utility of continued monitoring of at-risk populations.When a child screens positive or is judged to beat risk for ASD based on parent concern or physician observation, referral is required for further evaluation and treatment recommendations.
Well-validated assessment tools, such as the Autism Diagnostic Observation Schedule,8 and expert clinician judgment can establish a diagnosis and guide intervention recommendations. Acomprehensive diagnostic evaluation consists of the direct examination of social communication (eg, gesture use, quality and frequency of social initiations) and presence of any stereotyped or repetitive behavior and unusual sensory interests; standardized assessment yielding age-normed scores of intellectual ability, speech and language skills, and adaptive functioning (eg, communication, play, and daily living
skills); and parental report of the child’s developmental history. Standardized assessment tools provide comprehensive and replicable clinical information but require training and do not replace clinician judgment
Currently, there are no clinically validated biomarkers for ASD diagnosis at any age point, including the critical period of infancy. However, several general risk factors can be taken into consideration when assessing for ASD in young children. Younger siblings of children diagnosed with ASD have an approximately 20% risk for ASD and substantially higher rates of other developmental and behavioral difficulties. Boys are diagnosed 4 times as often as girls, although subtler symptom presentation in some girls may result in missed diagnoses. A number of additional risk factors have been proposed for ASD (eg, older fathers, prematurityat birth), but most await replication in large, population-based samples. If a child is diagnosed with ASD, medical evaluation can determine whether cooccurring conditions, such as sensory motor difficulties, hearing
problems, gastrointestinal symptoms, or seizures, are present. Genetic screening may identify known genetic syndromes that are associated with ASD (eg, fragile X syndrome). Routine magnetic resonance imaging to rule out other conditions is no longer generally recommended. The heterogeneity inherent in the expression of ASD with respect to symptom presentation and timing of onset complicates the diagnostic process and clinical decision-making but does not support a wait-and-see approach, despite a small number of cases that appear to remit with less intensive supports.
Children diagnosed as having ASD will need referral for individualized treatment.Across the United States, publicly funded early intervention programs conduct developmental screening for children 3 years and younger (ie, the Birth-to-Three program). If a developmental delay is confirmed, children are entitled to services through this system, often including developmental preschool, occupational therapy, speech therapy, and family support. However, evidence suggests intensive behavioral intervention, when implemented for more than 15 hours per week on a one-on-one basis for a year or longer using developmental and applied behavior analysis principles, is also needed to maximize outcomes across the critical
domains of communication,IQ, and adaptive function for young child ren with ASD. Combining parent coaching (teaching parents to use intervention techniques) with therapist-delivered behavioral interventions can further improve outcomes for young children and families. Despite emerging evidence of cost-effectiveness and long term efficacy,one-third of all children with ASD receive no intensive behavioral intervention. There are no evidence-based pharmaceutical interventions for treating core ASD symptoms, but medication can be used to treat comorbid conditions that emerge later, such as attention-deficit/hyperactivity disorder and anxiety. To summarize, timely diagnosis soon after symptom emergence facilitates beginning ASD-specific interventions that prepare these young children for increased participation in educational settings. It also sets the stage formeeting later developmental challenges in what is typically a lifelong condition.
Аuthors: Annette Estes, PhD; Tanya St. John, PhD; Stephen R. Dager, MD