Public schools are required by law to identify all children with disabilities, including those with autism spectrum disorder (AU) (IDEA, 2004). Early identification is key because early treatment leads to better outcomes (Dawson & Osterling, 1997; Eikeseth, Smith, Jahr, & Eldevik, 2007). Although it is often difficult to suggest to staff and parents that a child may have autism spectrum disorder, there is a significant risk associated with failing to recognize the disorder and provide intervention when it is present.
The process of evaluating for autism spectrum disorder 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 autism spectrum disorder 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.
- Autism spectrum disorder is not rare. In fact, it has “… more children than are affected by diabetes, AIDS, cancer, cerebral palsy, cystic fibrosis, muscular dystrophy, or Down syndrome—combined” (Autism Speaks, 2012).
- 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).
- Diagnosis at age 2 is accurate and stable over time (Charman et al., 2005; Eaves & Ho, 2004; Lord et al., 2006; Turner et al., 2006).
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. Indeed, Filipek et al. (1999) stress the importance of parent/caregiver input to the diagnostic process.
Critical areas to include in a developmental history are summarized below. Several autism screening and assessment tools incorporate components of a developmental history questionnaire. These are denoted with an asterisk (*) on the assessment tool table.
- Birth History
- Family History (immediate and extended)
- Medical History
- Developmental Milestones
Overview of Instruments
Accurate screening and diagnosis/identification 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. The information gathered during screening is incorporated in the comprehensive assessment process.
A number of tools are available for screening and diagnosis/identification of autism spectrum disorder. This section will provide a brief review of measures designed to capture descriptive information from parents/caregivers, staff, 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. Charak and Stella (2001–2002) identified seven instruments as screeners (ABC, ASIEP, CHAT, PDDST, STAT, ASQ, and the SCQ) and four instruments as diagnostic (ADOS, CARS, GARS, and the ASDS).
Instruments not included in Charak and Stella’s selective review are identified as screening or diagnostic based on the authors’ description. If the assessment has been updated since Charak and Stella’s publication, the updated version is included in this section. Several autism screening and diagnostic/identification tools incorporate components of a developmental history questionnaire.
The additional assessments included in this autism screening and assessment portion are: Autism Diagnostic Interview-Revised (ADI-R); Autism Observation Scale for Infants (AOSI); Autism Screening Instrument for Educational Planning – Third Edition (ASEIP-3); Autism-Spectrum Quotient (AQ); Checklist for Autism Spectrum Disorder (CASD); Childhood Autism Spectrum Test (CAST); Development Behavior Checklist – Autism Screening Algorithm (DBC-ASA); Developmental Checklist – Early Screen (DBC-ES); Early Screening of Autistic Traits (ESAT); Gilliam Autism Rating Scale – Third Edition (GARS-3); Krug Asperger’s Disorder Index (KADI); Modified Checklist for Autism in Toddlers, Revised with Follow-up (MCHAT-R/F); Monteiro Interview Guidelines for Diagnosing Asperger’s Syndrome (MIGDAS); Pervasive Developmental Disorders Screening Test – Second Edition (PDDST-II); Social Responsiveness Scale – Second Edition (SRS-2); and Screening Tool for Autism in Two-Year-Olds (STAT).
Note: All summary and research tables in the remainder of this section are from: Grossman, Aspy, and Myles (2009), Interdisciplinary evaluation of autism spectrum disorders: From diagnosis through program planning. Shawnee Mission, KS: Autism Asperger Publishing Company. All are used with permission. Some of the tables have been updated to include recent assessment information.
|Autism spectrum disorder is a medical diagnosis.||Currently, no medical tests can be used to diagnose autism spectrum disorder. The disorder is identified behaviorally.|
|If a student can pass the state exam and make passing grades, he or she does not have an educational need for special education.||Educational need extends beyond academics and includes communication, social, emotional, and adaptive skills.|
|Autism Spectrum Disorder, Level 1 means that an individual is high-functioning and, therefore, does not require special education support and services (e.g., specialized instruction).||Individuals with Autism Spectrum Disorder, Level 1 (formerly referred to as Asperger’s Disorder) have a pervasive developmental disorder. It is impossible to have a “pervasive” disorder and not be significantly impacted. While many of these individuals are highly intelligent and articulate, they do have significant impairments and most often require supports and services in order to make educational progress.|