It is recognised that an early diagnosis is important in improving outcomes in that effective strategies can only be put into place once the exact nature of the diagnosis is known.
Early intervention reduces stress within the family and helps to ensure that "problem" behaviours do not become entrenched- these behaviours become more difficult to manage as the child grows older.
An early diagnosis enables parents to be given appropriate genetic counselling to parents if they are contemplating having another child.
Autism cannot be diagnosed using physical tests, doctors instead rely on a range of screening and assessment tools which focus on communication skills, behaviour and relationships with others. Some of these tools rely on interviews with parents whilst others entail observing and assessing the child as well as feedback from parents.
Screening instruments
The checklist for autism in toddlers (CHAT) is screening instrument to be used by gps and health visitors at the 18-month developmental check-up. The checklist contains nine questions for parents and requires the gp or health visitor to make 5 observations as to the child's abilities with regard to joint attention, including pointing to show and gaze monitoring as well as pretend play.
The National Autistic Society's page on CHAT describes it as cheap, quick and easy to administer. Currently autism is rarely detected before the age of three and more extensive use of CHAT would go some way to reducing that threshold.
The checklist asks parents the following questions:
The doctor or health visitor is then asked to make the following observations-
Questions 2, 3 and 4 are considered to be most indicative of autism.
Any child who "fails" the CHAT should be tested again within four weeks. A second failure should result in a referral to a specialist clinic for diagnosis. CHAT is effective in identifying concerns but cannot be used for making a diagnosis.
A recent Medscape article on the diagnosis of autism spectrum disorders in the first three years of life features behaviours (from 6 months onwards) which (particularly in combination) may warrant referral and developmental surveillance as they may be precursors to an autistic spectrum disorder. The same article also points out that early diagnoses are often unstable. In one study it was reported that 22% of two year old children diagnosed with an autistic spectrum disorder did not have that disorder at the age of 4.
Diagnostic tools
A number of tools have been developed and refined to improve the accuracy of diagnoses. Of these, the best validated for achieving a conclusive diagnosis are the Diagnostic Interview for Social and Communication Disorders (DISCO) and the Autism Diagnostic Interview-Revised (ADI-R) both of which provide a structured framework for the assessment of developmental and behavioural functioning. The ADI is often used in conjunction with the Autism Diagnostic Observational Schedule (ADOS). The use of these tools requires a high degree of training.
The ADI-R on three main behavioural areas, quality of social interaction, communication and language and restricted and repetitive, stereotyped interests and behaviours. Social interaction looks at emotional sharing, offering and seeking comfort, social smiling and responding to other children. Communication and language looks at steotyped utterances, pronoun reversal and social usage of language. Repetitive and stereotyped interests and behaviours looks at unusaual preoccupations, hand and finger mannerisms, unusual sensory interests. Other areas such as self-injury and over-activity are also included
The assessment process consists of 93 questions which are asked of the caregiver. Each answer is rated from 0 ("behaviour of the type specified in the coding is not present") to 3 ("extreme severity" of the behaviour specified). A dignosis of autism is given when the scores in all three main areas exceed the specified cutoffs. The cutoff point for the social interaction section is 10, for restricted and repetitive behaviours the cutoff is 3 and for communication and language, the cutoff for verbal subjects is 8 and 7 for nonverbal subjects.
The ADI-R assessment can be administered to a parent or caregiver by a properly trained clinician in about 90 minutes.
The focus of ADOS is on social behaviour and communication. There are four different modules which a deployed according to age and level of verbal flunecy. Module 1 is used with children who "do not consistently use phrase speech", module 2 is for children who use phrase speech but are not particularly fluent, module 3 is used with fluent children and module 4 is used with fluent fluent adults. ADOS does not cater for nonverbal adolescents and adults.
During the assessment session the examiner will present the subject with a range of different activities. The response to each activity is recorded and rated. The ADOS has been described as giving doctors a structured and standardised way of observing and evaluationgg both communication and social behaviour. The Schedule should not be used on its own to provide a diagnosis but should be accompanied by information from other sources such as the ADI-R.
The DISCO is described as both a clinical and research instrument comprising a detailed, semi-structured interview to be used with "an informant who has known the person concerned well, preferably from infancy".
Disco can be used with children and adults of any age and any level of ability. It uses a dimensional approach which it is claimed is far more useful for prescribing how to help each individual than is arriving at a diagnostic category. Disco can also be useful in identifying conditions such as ADHD, tics, dyspraxia and catatonia-like disorders.
More information on DISCO can be found at the NAS website.
