By Dr Michelle Garnett & Prof Tony Attwood
We have often been asked: Will a full-day training on diagnostic assessment provide thorough training in the Autistic Diagnostic Observational Schedule, Second Edition (known as the ADOS)? Within their clinical practice, allied health may be asked by medical practitioners to provide an ADOS to determine if the person is on the autism spectrum.
For many years the ‘gold standard’ in the diagnosis of autism was considered to be the combination of two instruments, the Autistic Diagnostic Interview–Revised (ADI-R), and the ADOS. However, many health practitioners are not aware that the combination was considered to be the research standard, but only for classic autism, and only for definitions of autism in previous editions of the diagnostic manuals, prior to the Diagnostic and Statistical Manual for Mental Illness (DSM-IV-TR).
Of course, we do not expect that everyone has the time to scour the literature, to read the manuals for the diagnostic instruments available, and to know the current ‘gold standard’ for autism. However, we are lucky to be in the position, as clinical psychologists who have specialised in autism over the past 30 and 50 years respectively, to be able to keep a finger on the diagnostic pulse of autism.
It may surprise you to know that, because the diagnosis is subjective, that is, there no biological markers for autism that we know of, the current ‘gold standard’ is a clinician assigned diagnosis, as provided by experienced clinicians. There is no tool that can diagnose autism. An experienced clinician keeps abreast of the current diagnostic and other tools available and chooses the best tools, based on the referral information, the age, the differential diagnoses, and the gender of the person to be assessed.
Some presentations of autism are more subtle, for example, many people who are verbal and have at least average intelligence, especially if they use camouflaging as a coping strategy, have a subtle presentation of autism. When this is the case, the ADOS may be used as part of a diagnostic assessment, but often would not be the first choice.
Diagnostic assessment tools are evaluated using a standardisation sample, which is a group of people chosen because they represent the people that the tool will be used to assess. The group needs to be representative, and large enough to give statistical weight to the results. In the development of Module 4, the part of the ADOS that would be used to assess a verbal adult of at least average intelligence, the sample was only thirty people, and of this sample only five were female. The algorithms for determining if the person has autism are based on previous definitions of autism and the predictive validity of the ADOS was only approximately 50%.
A recent study (Langmann, et al, 2017) examined the ADOS, Module 4, in a sample of 356 sample, 12 to 68-year-olds. Results showed that the ADOS had low diagnostic accuracy for females, older individuals and individuals with personality disorders or high intellectual ability.
We strongly encourage diagnosticians seeking to increase their skill in the assessment of adults who may have autism, to seek training in what data to collect, i.e. what to look for, and the best methods to collect the data. We recommend that before seeking specific training see many people who are, and who are not, on the autism spectrum. Once trained in the diagnostic assessment for autism, we highly recommend receiving clinical supervision for the first few cases.
We encourage clinical psychologists, GPs with an interest in autism and adult psychiatrists to seek training in the diagnosis of autism, in all its forms and variations across age, gender, verbal ability and IQ. For example, it is currently the case that adult women have seen an average of four clinicians before they receive an accurate diagnosis of autism. In the meantime, they have been mislabelled, received misinformation about their conditions, and have missed out on accurate and appropriate interventions to assist them with their self-understanding and overall mental health.
Langmann et al (2017). Research in Autism Spectrum Disorders 34 pp 34-43