How is it assessed?

Cause

There has been substantial research into the causes of Autism spectrum disorders (ASD). Studies have shown that many major brain structures are involved in autism. Some research is focusing on the role of certain chemicals (neurotransmitters) such as serotonin which are secreted in the brain. Evidence also points to genetic factors playing a role in the causes for ASD.

Multiple reviews and studies have failed to establish any links between vaccines and ASD.

Diagnosing ASD

The evidence shows that intensive early intervention results in improved outcomes in most young children with ASD. Behavioural characteristics are the basis of a diagnosis. Some of the characteristic behaviours of ASD may be apparent in the first few months or they may appear at any time during the early years. Parents/carers often notice very early that “something is not quite right”.

The diagnosis is a two-stage process. The first stage involves developmental screening, the second stage entails a comprehensive evaluation.

There are different criteria for diagnosing ASD e.g. using the International Classification of Diseases (ICD 10) or “Gillberg and Gillberg” etc. The criteria used for diagnosis is not important – the fact that a formal diagnosis has been made is the important consideration.

IQ can be assessed from almost any age. The WPPSI (Wechsler Pre-school and Primary Scale of Intelligence) is thought to be a robust measure of intelligence and is used from age 3. Prior to age 3 the Bayley Scales of Infant Development can be used from 1 month to age 2½, which will not give IQ scores per se but will allow the scoring of developmental indexes which are equivalent to IQ’s. The Kaufman Assessment Battery for Children from age 2½ to age 12½ and the Stanford-Binet Intelligence Scale from age 2 to age 18 are also sometimes used but not as widely as the Bayley and WPPSI.  The Bayley scales are used more by educational psychologists than clinical psychologists and provide a General Conceptual Ability score which is slightly different to IQ but an indicator of cognitive function.

Screening

Screening instruments rely on parent responses to a questionnaire and some rely on a combination of parent report and observation. They serve to assess the need for referral for possible diagnosis of ASD but may not identify some children with ASD, such as those with high-functioning autism or Asperger’s Syndrome.

Several screening instruments have been developed to quickly gather information about a child's social and communicative development -:

• Checklist of Autism in Toddlers (CHAT)
• The modified Checklist for Autism in Toddlers (M-CHAT)
• The Screening Tool for Autism in Two-Year-Olds (STAT)
• Social Communication Questionnaire (SCQ) specifically for children 4 years of age and older.
• The Developmental, Diagnostic and Dimensional Interview (3Di) Screening Tool

The Autism Spectrum Screening Questionnaire (ASSQ) and the Childhood Asperger Syndrome Test (CAST) are two screening instruments that are reliable for identification of school-age children with possible Asperger’s Syndrome or higher functioning autism.

If after screening, any of the possible indicators of ASD are identified, further evaluation is indicated.

Comprehensive Diagnostic Evaluation

The goal is to accurately diagnose ASD and guide interventions. There is no diagnostic test for ASD and the diagnosis can only be confirmed after extensive evaluation by a multidisciplinary team that includes a psychologist, a paediatrician, a psychiatrist, a speech therapist or other professionals who diagnose children with ASD.

Tools developed specifically for diagnosing autism are often used and include the Autism Diagnosis Interview-Revised (ADI-R), the Autism Diagnostic Observation Schedule (ADOS-G) and the Childhood Autism Rating Scale (CARS). The ADI-R for instance is a structured interview that contains over 100 items and is conducted with a caregiver. It consists of four main factors -:

• the child's communication,
• social interaction,
• repetitive behaviours; and
• age-of-onset symptoms.

Other tests include a formal hearing evaluation and genetic and metabolic screening. Imaging studies such as Magnetic Resonance Imaging (MRI) scans and laboratory investigations may show abnormalities, however no finding has characterized all people with autism and the results vary with each individual.

For a formal diagnosis, symptoms in each one of the areas of -:

• communication,
• socialization; or
• restricted behavior

must be present by the age of 3.