This process of forming "best-estimate clinical diagnoses" has long been considered the gold standard, but a new study demonstrates that these diagnoses are widely variable across centres, suggesting that this may not be the best method for making diagnoses.
"Clinicians at one centre may use a label like Asperger syndrome to describe a set of symptoms, while those at another centre may use an entirely different label for the same symptoms. This is not a good way to make a diagnosis," says Doctor Catherine Lord of the Institute for Brain Development, a partnership of Weill Cornell Medical College, NewYork-Presbyterian Hospital and Columbia University Medical Center. "Autism spectrum disorders are just that - a spectrum of disorders. Instead of using subcategories, it would be better to simply report the results from agreed-upon tests and scales. This approach would provide more consistent and accurate information about individual patients."
In the new study researchers studied about 2,100 people between the ages of 4 and 18 who were given a diagnosis of autism spectrum disorder by clinicians at 12 university-based centres. The participants were recruited from the Simons Simplex Collection, a multi-site project aimed at studying de novo genetic variations in families affected by autism spectrum disorders.
The clinicians, who are experts in autism spectrum disorders, received training on how to administer and score the same set of cognitive tests and standardised instruments assessing social and communication skills and repetitive behaviour, including the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview - Revised (ADI-R). However, they received no specific training in making best-estimate clinical diagnoses. They used the Diagnostic and Statistical Manual of Mental Disorders – IV – text revision (DSM-IV-TR) to classify individuals into three categories of varying severity: autistic disorder, pervasive developmental disorder - not otherwise specified (PDD-NOS), and Asperger syndrome.
The researchers found that diagnoses of specific categories of autism spectrum disorder varied dramatically from site to site across the country. For instance, clinicians at one site gave only a diagnosis of autistic disorder, while clinicians at other sites gave that diagnosis to fewer than half of the participants. The proportion of individuals receiving a diagnosis of Asperger syndrome ranged from zero to nearly 21 per cent across sites. These site differences were the second most important factor accounting for variation in the diagnoses (after social and communication deficits). However, the individuals with autism spectrum disorders did not vary significantly across sites in terms of their demographic information or developmental and behavioural characteristics, as measured by standardised instruments.
MEDICA.de; Source: Cornell University