Public schools are required by law to identify all children with disabilities, including those with autism spectrum disorder (ASD)/autism (AU) (IDEA, 2004). Early identification is key because early treatment leads to better outcomes (Dawson & Osterling, 1997; Dawson et al., 2010; Eikeseth, Smith, Jahr, & Eldevik, 2007; Kasari, Gulsrud, Wong, Kwon, & Locke, 2010). Although it is often difficult to suggest to staff and parents that a child may have ASD, there is a significant risk associated with failing to recognize the disorder and provide intervention when it is present.
The process of evaluating for ASD is complex and cannot be reduced to a single score from a single test. Freeman, Cronin, and Candela (2002) highlight that “rating scales were not designed to be used in isolation to make a diagnosis. They are useful to the clinician, but are only one source of qualitative information for a comprehensive clinical assessment” (p. 148). Accurate identification of ASD requires analysis of both qualitative and quantitative data from a number of sources. As such, a quality assessment is dependent on the clinician—the most important component of any evaluation process.
This section discusses the importance of obtaining a thorough developmental history and reviews ASD screening and assessment tools.
Did You Know?
- Autism spectrum disorder is not rare. Current diagnostic prevalence rates are estimated at 1 in 59 (Baio et al., 2018).
- A growing body of research suggests that autism spectrum disorder can be accurately diagnosed by age 2 (Centers for Disease Control, 2014; Charman & Baird, 2002). However, the average age of diagnosis in the U.S. remains around 4-years-old (Lord et al., 2006). Black and Hispanic children are diagnosed years later than their White peers (Baio et al., 2018), as are children from low income families (Durkin et al., 2017).
- Diagnosis at age 2 is generally accurate and stable over time (Baird et al., 2008; Charman et al., 2005; Crais & Watson, 2014; Eaves & Ho, 2004; Lord et al., 2006; Turner et al., 2006).
- Subtypes such as Autistic Disorder, Asperger Syndrome, and Pervasive Developmental Disorder Not Otherwise Specified (PDD NOS) are no longer delineated within the DSM-5 (APA, 2013). Rather, the updated diagnostic criteria consolidate these into an umbrella diagnosis of “autism spectrum disorder”. Two categories of symptoms are required: (a) persistent deficits in social communication/interaction, and (b) restricted, repetitive patterns of behavior. Sensory issues, including hyper- or hypo-reactivity to stimuli or unusual interests in stimuli, are a symptom contained within the restricted/repetitive behavior category. Severity levels are assigned for each of the two categories and are based on the level of support needed for daily functioning. Specifiers are used to identify intellectual ability, language level, and known genetic and/or medical conditions within the ASD diagnosis.
- Though the DSM-5 (APA, 2013) yields a clinical diagnosis and the IDEA (2004) yields an educational classification, there are many similarities between the two. For example, both refer to the impact of ASD on daily functioning, acknowledge a range of difficulties, acknowledge that impairments emerge in early development, include core difficulties in verbal and nonverbal social communication, and include core difficulties in social interaction.
Autism is classified as a “Neurodevelopmental Disorder” by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5; American Psychiatric Association, 2013); therefore, accurate assessment must include a thorough developmental history. Developmental history is best collected through an in-person interview with the child’s parents/caregivers. In fact, the importance of parent/caregiver input to the diagnostic process cannot be overstated (Filipek et al., 1999; Saulnier & Ventola, 2012).
Critical areas to include in a developmental history are listed below:
- Birth History
- Family History (immediate and extended)
- Pervasive Developmental Disorders
- Genetic or Medical Disorders
- Learning Disorders
- Emotional/Behavioral Disorders
- Medical History
- Medical Conditions (e.g., seizures, allergies, asthma, head injury/trauma)
- Sensory Differences
- Previous Evaluations/Other Diagnoses
- Developmental Milestones
- History of Regression or Interruption of Development
- History of Interventions
Overview of Instruments
Accurate screening and diagnosis/identification of any condition, including ASD, requires collecting and assimilating data from a variety of sources using multiple methods. As with all data, the information collected must subsequently be interpreted. Experienced clinicians never rely strictly on a screening or diagnostic instrument. Although assessment tools can provide valuable information, no tool interprets itself.
Efforts have been made to distinguish between screening and diagnostic tools. For example, Charak and Stella (2001–2002) state that, “Screening instruments are intended to help clinicians identify children who present with developmental delays and/or atypical behavior for whom a diagnosis in the autistic spectrum may be considered … [those] who should be referred for a more intensive diagnostic evaluation” (p. 6). The term “diagnostic” instrument is misleading because no single instrument constitutes a sufficient basis for a diagnostic decision. In practice, there is no distinct line where screening ends and diagnostic assessment begins. Moreover, many screening instruments, particularly those that are used in universal/level 1 screening, prioritize sensitivity over specificity and may yield false positives (Zwaigenbaum et al., 2015). Therefore, it is important that information gathered during screening is incorporated into the comprehensive assessment process.
A number of tools are available for screening and diagnosis/identification of ASD. This section will provide a brief review of measures designed to capture information from parents/caregivers, school personnel, clinicians, and the student.
Autism Spectrum Screening and Diagnostic/Identification Tools
The autism screening and diagnostic/identification tools included are the best known and most widely used instruments available in both practice and research. The instruments included in this autism screening and assessment section are:
- Asperger Syndrome Diagnostic Scale (ASDS)
- Autism Diagnostic Interview-Revised (ADI-R)
- Autism Diagnostic Observation Schedule- Second Edition (ADOS-2)
- Autism Observation Scale for Infants (AOSI)
- Autism Screening Instrument for Educational Planning – Third Edition (ASEIP-3) and the Autism Behavior Checklist (ABC)
- Autism-Spectrum Quotient (AQ)
- Autism Spectrum Rating Scales (ASRS)
- Checklist for Autism Spectrum Disorder (CASD)
- Childhood Autism Rating Scale- Second Edition (CARS-2)
- Childhood Autism Spectrum Test (CAST)
- Development Behavior Checklist – Autism Screening Algorithm (DBC-ASA) and Early Screen (DBC-ES)
- Early Screening of Autistic Traits (ESAT)
- Gilliam Asperger’s Disorder Scale (GADS)
- Gilliam Autism Rating Scale – Third Edition (GARS-3)
- Modified Checklist for Autism in Toddlers, Revised with Follow-up (MCHAT-R/F)
- Monteiro Interview Guidelines for Diagnosing the Autism Spectrum, Second Edition (MIGDAS-2)
- Parent’s Observations of Social Interactions (POSI)
- Screening Tool for Autism in Toddlers and Young Children (STAT)
- Social Communication Questionnaire (SCQ)
- Social Responsiveness Scale – Second Edition (SRS-2).