Autism Spectrum Disorder a clinical
diagnosis that is typically made by a physician based off reported and directly observed behavior in the affected individual. According to the updated diagnostic criteria in the
DSM-5-TR, in order to receive a diagnosis of Autism Spectrum Disorder, one must present with “persistent deficits in social communication and social interaction” and “restricted, repetitive patterns of behavior, interests, or activities.” These behaviors must begin in early childhood and affect one’s ability to perform everyday tasks. Furthermore, the symptoms must not be fully explainable by
intellectual developmental disorder or
global developmental delay. There are several factors that make Autism Spectrum Disorder difficult to diagnose. First off, there are no standardized imaging, molecular or genetic tests that can be used to diagnose ASD. Additionally, there is a lot of variety in how ASD affects individuals. The behavioral manifestations of ASD depend on one’s developmental stage, age of presentation, current support, and individual variability. Lastly, there are multiple conditions that may present similarly to Autism Spectrum Disorder, including
intellectual disability,
hearing impairment, a
specific language impairment such as
Landau–Kleffner syndrome.
ADHD,
anxiety disorder, and
psychotic disorders. Furthermore, the presence of autism can make it harder to diagnose coexisting psychiatric disorders such as
depression.
Ideally the diagnosis of ASD should be given by a team of clinicians (e.g. pediatricians, child psychiatrists, child neurologists) based on information provided from the affected individual, caregivers, other medical professionals and from direct observation. Evaluation of a child or adult for Autism Spectrum Disorder typically starts with a
pediatrician or
primary care physician taking a developmental history and performing a physical exam. If warranted, the physician may refer the individual to an ASD specialist who will observe and assess cognitive, communication, family, and other factors using standardized tools, and taking into account any associated
medical conditions. A pediatric
neuropsychologist is often asked to assess behavior and cognitive skills, both to aid diagnosis and to help recommend educational interventions. Further workup may be performed after someone is diagnosed with ASD. This may include a
clinical genetics evaluation particularly when other symptoms already suggest a genetic cause. Although up to 40% of ASD cases may be linked to genetic causes, it is not currently recommended to perform complete genetic testing on every individual who is diagnosed with ASD. Consensus guidelines for genetic testing in patients with ASD in the US and UK are limited to high-resolution chromosome and
fragile X testing.
Metabolic and
neuroimaging tests are also not routinely performed for diagnosis of ASD.he age at which ASD is diagnosed varies. Sometimes ASD can be diagnosed as early as 14 months, however, a reliable diagnosis of ASD is usually made at the age of two years. Diagnosis becomes increasingly stable over the first three years of life. For example, a one-year-old who meets diagnostic criteria for ASD is less likely than a three-year-old to continue to do so a few years later.Additionally, age of diagnosis may depend on the severity of ASD, with more severe forms of ASD more likely to be diagnosed at an earlier age. Issues with access to healthcare such as cost of appointments or delays in making appointments often lead to delays in the diagnosis of ASD. In the UK the National Autism Plan for Children recommends at most 30 weeks from first concern to completed diagnosis and assessment, though few cases are handled that quickly in practice. Lack of access to appropriate medical care, broadening diagnostic criteria and increased awareness surrounding ASD in recent years has resulted in an increased number of individuals receiving a diagnosis of ASD as adults. Diagnosis of ASD in adults poses unique challenges because it still relies on an accurate developmental history and because autistic adults sometimes learn coping strategies (known as ‘camouflaging’) which may make it more difficult to obtain a diagnosis.
The presentation and diagnosis of Autism Spectrum Disorder may vary based on sex and gender identity. Most studies that have investigated the impact of gender on presentation and diagnosis of Autism Spectrum Disorder have not differentiated between the impact of sex versus gender. There is some evidence that autistic women and girls tend to show less repetitive behavior and may engage in more camouflaging than autistic males. Camouflaging may include making oneself perform normative facial expressions and eye contact. Differences in behavioral presentation and gender-stereotypes may make it more challenging to diagnose autism spectrum disorder in a timely manner in females. A notable percentage of autistic females may be misdiagnosed, diagnosed after a considerable delay, or not diagnosed at all.
Considering the unique challenges in diagnosing ASD using behavioral and observational assessment, specific US practice parameters for its
assessment were published by the American Academy of Neurology in the year 2000, the American Academy of Child and Adolescent Psychiatry in 1999, and a consensus panel with representation from various professional societies in 1999. The practice parameters outlined by these societies include an initial screening of children by general practitioners (i.e., “Level 1 screening”) and for children who fail the initial screening, a comprehensive diagnostic assessment by experienced clinicians (i.e. “Level 2 evaluation”). Furthermore, it has been suggested that assessments of children with suspected ASD be evaluated within a developmental framework, include multiple informants (e.g., parents and teachers) from diverse contexts (e.g., home and school), and employ a multidisciplinary team of professionals (e.g., clinical psychologists,
neuropsychologists, and psychiatrists).
As of 2019, psychologists wait until a child showed initial evidence of ASD tendencies, then administer various psychological assessment tools to assess for ASD. Among these measurements, the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (uADOS) are considered the “gold standards” for assessing autistic children. The ADI-R is a semi-structured parent interview that probes for symptoms of autism by evaluating a child’s current behavior and developmental history. The ADOS is a semistructured interactive evaluation of ASD symptoms that is used to measure social and communication abilities by eliciting several opportunities for spontaneous behaviors (e.g., eye contact) in standardized context. Various other questionnaires (e.g., The
Childhood Autism Rating Scale,
Autism Treatment Evaluation Checklist) and tests of cognitive functioning (e.g., The Peabody Picture Vocabulary Test) are typically included in an ASD assessment battery. The
diagnostic interview for social and communication disorders (DISCO) may also be used.