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Due to the lack of any specific identification of the cause or definitive physiological criteria of ASD, there is no single test that can diagnose a child or individual for ASD. The Diagnostic and Statistical Manual of Developmental Disorders (DSM-5) prescribes the necessary criteria to evaluate and diagnose Autism and Spectrum Disorder (ASD) and Social Communication Disorder (SCD) through a comprehensive behavioral and developmental assessment. This is the most recent and updated classification system, published in 2013.
Another major diagnostic classification system currently in use is that prescribed by the International Classification of Diseases version 10 (ICD-10), published in 1993.
Either the ICD-10 or the DSM-5 can be used for diagnosis, as long as the classification system actually used is recorded.
Under ICD-10, autism is defined as a pervasive developmental disorder (PDD), or a group of disorders characterized by:
- The presence of abnormal or impaired development that is manifest before the age of 3 years; and
- Qualitative abnormalities in:
- Reciprocal social interactions and in patterns of communication; and
- Restricted, stereotyped, repetitive repertoire of interests and activities
These qualitative abnormalities are pervasive features of the individual’s functioning in all situations. A range of other nonspecific problems may also be common, including phobias, sleeping and eating disturbances, temper tantrums, and (self-directed) aggression.
Under DSM-5, the concept of an autistic spectrum disorder (ASD) is used rather than a pervasive developmental disorder (PDD). One of the basic differences between these two is that the former makes use of the “autism spectrum” rather than types and subtypes Thus, previous subtypes and classifications recognized in DSM-IV are no longer used. DSM-5 also added the following symptoms and diagnostic criteria:
- New clinical signs of stereotypical speech
- Hyperreactivity or Hyporeactivity to sensory input, or interest in sensory aspects of the environment
But the basic diagnostic criteria under DSM-5 are:
- Persistent deficits in social communication and social interaction across multiple contexts; and
- Restricted, repetitive patterns of behavior, interests, or activities.
Diagnosis is generally made based on observed patterns of behavior. It is imperative that diagnosis be made by trained experts or a team of specialists – the diagnosis of ASD can be complicated and is considered a highly specialized area involving multiple evaluations and tests. Some of the specialists you might have to work with include child psychologists, child psychiatrists, speech pathologists, developmental pediatricians, pediatric neurologists, audiologists, physical therapists, and special education teachers.
A comprehensive evaluation is, of course, ideal. Not only will it give you a more accurate diagnosis, doing so will enable you to determine the best type of treatment your child needs, depending on the types and severity of symptoms he or she is experiencing. Some of the tests and evaluations you may expect include:
- Parent interview
- Medical exam
- Hearing test
- A period of observation in a variety of settings
- Lead screening
- Speech and language evaluation
- Cognitive testing
- Adaptive functioning assessment
- Sensory-motor evaluation