Autism is a developmental disorder characterised by impairments in social interaction, communication and behaviour. The estimated prevalence of autism is 1–2 per 1000 children, and up to six per 1000 for all autism spectrum disorders (ASDs),1,2 a category that also includes Asperger syndrome and “pervasive developmental disorder not otherwise specified”. The causes of ASDs are largely unknown. Clustering of diagnoses in families suggests a genetic component and a high degree of heritability,3 but the possible mechanisms are poorly understood. Information about biological characteristics in early childhood is also severely lacking.
ASDs are diagnosed using clinical criteria described in the International classification of mental and behavioural disorders (ICD-10) classification system4 or the Diagnostic and statistical manual of mental disorders (DSM-IV).5 Symptoms are often noticed by 12 months of age,6 but affected individuals show large differences in their presentation.7 Diagnosis usually occurs around 3–4 years of age when social and communication milestones are not achieved. Apart from the number and pattern of criteria present, there are no other measurable physical or psychological markers to distinguish between the ASD diagnoses. Although the diagnostic criteria seek to distinguish between autism and Asperger syndrome on the basis of early developmental characteristics (such as language development), in practice there is often little to distinguish the autism and Asperger profiles, as many children with autism develop language.5,8
The prevalence of ASDs has increased globally for the past two decades.9,10 It is unknown to what degree different factors are having an impact, such as new diagnostic practices, younger ages at diagnosis, increased awareness and diagnostic training opportunities for professionals, increased media reporting, and heightened awareness and pursuit of diagnoses by parents with concerns about their child’s development. In the absence of explanation, families and the general public remain concerned at the increasing number of diagnoses, as do clinicians and service providers who are under-resourced to cope adequately with the increasing demands associated with assessments, case management, service provision and education.
Over the past 20 years, the number of new diagnoses per year in Western Australia has increased nearly 20-fold, and now, more than 200 children are newly diagnosed with an ASD each year.11,12 Assessment centres and service providers have become highly pressured, resulting in lengthy waiting periods for school-aged children, and a shift towards private practice for more rapid assessments (Box 1). Each year, in addition to those who receive an ASD diagnosis, a similar number of children who are referred for assessment do not present with the required number of criteria to receive a formal diagnosis within the spectrum. This represents a significant developmental health issue that demands urgent investigation into the antecedents of, and explanations for, the observed increases.
In 1991, a Central Diagnostic Panel, consisting of eight clinicians representing different organisations and disciplines, was established to encourage a uniform approach to diagnostic decisions, service eligibility, reporting requirements and assessor training for ASD assessments and services to children throughout WA.13 At that time, less than 20 people per year were diagnosed with an ASD.11 As the number of referrals and diagnoses increased during the 1990s, so did the need for a more formal arrangement for streamlining assessments and eligibility requirements. In 1997, the Disability Services Commission (DSC) was nominated as the primary agency to distribute government early-intervention funding for children diagnosed with ASDs in WA. For children with an ASD diagnosis to be accepted as eligible for consideration of early intervention, diagnoses must now incorporate assessments by a team of three independent health professionals (a paediatrician or psychiatrist, a psychologist, and a speech pathologist) (Box 2). Assessments for adolescents (aged 12–17 years) and adults are required to be carried out by a clinical psychologist, a paediatrician (for adolescents) and/or a psychiatrist, and to include a formalised speech pathology assessment, if needed. For each assessment, a standardised cognitive or developmental instrument, an adaptive behaviour assessment, a speech assessment, and the current DSM criteria are used (Box 3). A supplementary assessment of family functioning by a social worker is used at one institution.
This protocol has been enhanced and strengthened in recent years using input from diagnosing clinicians and relevant support agencies throughout WA. Regular discussion occurs at meetings of the Western Australian Autism Diagnosticians’ Forum (WAADF; see below) to ensure efficient management of referrals, assessments, diagnoses, eligibility, and access to services across the state. To be recognised as an experienced assessor, a clinician must demonstrate specialty skills and knowledge in the area of autism and adhere to the assessment and diagnostic reporting standards and procedures identified by the DSC. These are the same standards and procedures that are published and recommended by the WAADF.13
The DSM criteria (as currently set out in the fourth edition, text revised version [DSM-IV-TR])5 are central to the diagnostic process and are supplemented with assessments of language, cognitive or developmental ability and adaptive behaviour. Alternative explanations for the observed symptoms, including hearing deficits or fragile X syndrome, are also considered. The diagnostic instruments typically include one or more of the following standardised instruments, depending on the person’s age, abilities and test compliance: the Griffiths Mental Development Scales,14 Bayley Scales of Infant Development,15 Stanford–Binet Intelligence Scale,16 Wechsler Intelligence Scale for Children,17 Wechsler Preschool and Primary Scale of Intelligence18 or the Reynell–Zinkin Scale.19 If the children are non-verbal, the Leiter International Performance Scale20 may be used. Additionally, the Vineland Adaptive Behavior Scales21 and the Clinical Evaluation of Language Fundamentals22 and/or a Peabody Picture Vocabulary Test23 are commonly used. The Autism Diagnostic Observation Schedule24 and the Autism Diagnostic Interview — Revised,25 which are intended for use by trained clinicians, are often used in comprehensive ASD evaluations. The Social Communication Questionnaire,26 a screening questionnaire based on the original Autism Diagnostic Interview — Revised, is occasionally included in the diagnostic process.
Since November 1998, quarterly education and discussion forums have been held among clinicians to review standards, processes and clinical issues in the assessment of ASDs in WA. Membership is open to clinicians and other interested parties from any sector. Membership is voluntary, but individuals are encouraged to register in order to keep abreast of current practices. In 2006, the WAADF had 87 financial individual and organisational members. The disciplines of paediatrics, psychology, speech pathology, education and disability management are represented at meetings, and most attendees are metropolitan-based.
In 2004, the WAADF became incorporated, and now recommends standards for assessment procedures throughout the state (http://www.waadf.org.au). In addition, the WAADF informs practitioners of service delivery changes and new developments in assessment processes, facilitates the interpretation of diagnostic criteria, and provides an opportunity for case discussion and presentation of research findings. The WAADF has produced booklets documenting current diagnostic assessment strategies. These are available in various versions directed at parents, clinicians and service providers.13
A statewide autism register was initiated in 1999 to monitor the number of people receiving a new ASD diagnosis each year.12 Financial assistance for the register has been provided by the health, disability and education sectors of local government. The register activities are supported through the WAADF, which ensures that clinicians are updated on changes and current progress.
Annual comparisons are made between the number of cases received at the register and the number of cases diagnosed at major centres and private practices. Missed cases identified by comparing the diagnostic information are added annually as anonymous entries. Information is not collected on people whose condition is diagnosed outside WA and who later take up residence in WA.
Between 1999 and 2005, more than 1440 people were recorded on the register, averaging over 200 new diagnoses a year. Parental permission to store confidential information was received in 41% of all cases, the remainder being anonymous entries, with year of birth and sex attached to the diagnostic information. Confidential information is stored securely. It is used to avoid the collection of double entries, and helps to communicate with clinicians in the event of missing or unclear data. It is estimated that the register collects most new diagnoses made on children in WA, given the small number of pathways to assessments and services that exist. The number of missed cases is difficult to estimate, as the register uses all known pathways to collect cases, but any missed cases would most likely be in older children or adolescents who are diagnosed through private practice, have mild ASD symptoms, have other primary diagnoses, or move out of WA after being assessed. A significant number of adults who have a mental and social incapacity that may be best explained by an ASD may also remain undiagnosed in the community and would not be accounted for in the register numbers.
The initiatives described here for developing consistent autism assessment methods and monitoring new cases are unique to Australia, and WA is one of few places internationally to develop uniform assessment and reporting methods within a specific region.27 The implementation of these endeavours means that WA can create consistency within the diagnostic process, facilitate clearer assessment and service intervention pathways, monitor the number of people diagnosed, observe changes over time, and provide population-based data for research purposes. These developments represent a strong commitment by local clinicians to maintaining high-quality diagnostic practices.
A central website was developed to consolidate information about WAADF, the WA autism register, local autism research projects, and other autism information (http://www.autismwa.org.au). A collaborative clinical and research working environment has emerged that promotes clear diagnostic processes and supports local autism research. These endeavours can be well utilised in future years to collect research data and interpret findings using information about diagnostic trends. Aspects of the WA practices may be useful as a model in other areas where effective diagnostic and monitoring strategies for ASDs are needed.
1 Proportion of non-government-funded autism spectrum disorder diagnoses in Western Australia, 1999–2005
3 Summary of regular team assessment details for autism spectrum disorder diagnoses in Western Australia for children aged up to 12 years
Paediatric/psychiatric assessments
General physical and neurodevelopmental examination, including hearing
Comprehensive developmental history, with an emphasis on global functioning and achievement of developmental milestones, using parent/caregiver interviews and a review of available case history information
Comprehensive medical history with an emphasis on excluding other medical conditions that may contribute to the current presentation
Laboratory testing
Review of past and current developmental strengths and needs
Review of past and current assessments of socialisation, communication and behaviour
Arrangement for psychiatric assessment if needed
Interviews with other relevant people if necessary (eg, teachers, child care staff and therapists)
Formal and/or informal testing of speech and language skills
Functional evaluation of communication skills in various relevant environments
Developmental history, with an emphasis on communication development, resulting from interviews with parents/caregivers and a review of available case history information
Review and assessment of past and current abilities, strengths and needs in the areas of language, social communication and play
Review and assessment of current testing results in terms of diagnostic criteria
Interviews with other relevant people if necessary (eg teachers, child care staff, other therapists)
Observation in the home, educational or broader social settings as necessary
Formal assessment of intellectual functioning/development or a review of assessments made within the past 2 years. If a standardised assessment is not possible, informal assessment techniques are used to estimate intellectual functioning
Standardised assessment of adaptive functioning for pre-primary-school-aged children
Developmental history, with an emphasis on behavioural and adaptive functioning, relevant background information, history and context of the family, using parent/caregiver interviews and a review of available case history information
Review and assessment of past and current developmental abilities, strengths and needs
Review and assessment of current testing results in terms of the diagnostic criteria (taking into account the systematic impact on the child’s behaviour)
Interviews with other relevant people if necessary (eg, teachers, child care staff, and therapists)
Observation in the home, educational or broader social settings as necessary
Social work assessment (undertaken only at the State Child Development Centre)
Observation in the home, educational or broader social settings as necessary, in order to assess family functioning using structured and non-structured interviews and questionnaires
Assessment of family expectations of the diagnostic process and post-diagnostic period
Assessment of family strengths and weaknesses, including support structures, mental health, stressors, resilience and finance
Support and advocacy for the child and family
Attendance at the multidisciplinary team meeting and provision of a report
Subsequent support of the family in the post-diagnostic period (eg, advocacy for services, entitlements for special payments, grieving process in relation to the diagnosis)
Abstract
Autism spectrum disorders (ASDs) are severe developmental conditions that require specialised intervention and lifelong support.
Recent increases in ASD prevalence have prompted new initiatives in Western Australia to improve the consistency of assessments and to more accurately monitor diagnostic trends within the population.
WA has implemented statewide guidelines for the assessment of ASDs, has developed an open forum for clinicians to discuss issues relating to the assessment process, and supports a statewide register of newly diagnosed cases.
These initiatives have led to improved consistency across assessments, allowed analysis of diagnoses over time, and promoted cohesiveness among autism assessors.
These strategies potentially provide an alternative model for other states and territories that wish to strengthen and assimilate ASD assessments.