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Saturday, October 24, 2015

Overdiagnosis in Some Cases?

Uncertainty is a major theme of The Politics of Autism.

At Autism, Stephen J. Blumberg and colleagues have an article titled "Diagnosis Lost: Differences Between Children Who Had and Who Currently Have an Autism Spectrum Disorder Diagnosis." The abstract:
Autism spectrum disorder diagnoses sometimes change due to misdiagnosis, maturation, or treatment. This study uses a probability-based national survey—the Survey of Pathways to Diagnosis and Services—to compare currently diagnosed (n = 1420) and previously diagnosed (n = 187) children aged 6–17 years based on retrospective parental reports of early concerns about their children’s development, responses to those concerns by doctors and other healthcare providers, the type of provider who made the first autism spectrum disorder diagnosis, and the autism spectrum disorder subtype diagnoses received (if any). Propensity score matching was used to control for differences between the groups on children’s current level of functioning and other current characteristics that may have been related to diagnosis loss. Approximately 13% of the children ever diagnosed with autism spectrum disorder were estimated to have lost the diagnosis, and parents of 74% of them believed it was changed due to new information. Previously diagnosed children were less likely to have parents with early concerns about verbal skills, nonverbal communication, learning, and unusual gestures or movements. They were also less likely to have been referred to and diagnosed by a specialist. Previously diagnosed children were less likely to have ever received a diagnosis of Asperger’s disorder or autistic disorder.
From the article:
Overdiagnosis may also occur if ASD diagnoses are substituted for other learning disabilities because of the availability of greater resources for treatment of ASD (Shattuck, 2006). Parents in this study confirmed that some children who reportedly did not have ASD—approximately one in four who lost their ASD diagnosis or 3% of all school-aged CSHCN ever diagnosed with ASD—were given the diagnosis due to their need for services.
Shattuck PT (2006) The contribution of diagnostic substitution to the growing administrative prevalence of autism in the US special education. Pediatrics 117(4): 1028–1037
 That observation is consistent with The Politics of Autism,  where I write:
Once parents get over their initial denial, they have strong reason to seek a diagnosis of ASD for troubled children, since it can trigger thousands of dollars in assistance. Allen Frances says: “Having the label can make the difference between being closely attended to in a class of four versus being lost in a class of 40. Kids who need special attention can often get it only if they are labeled autistic.” Roy Grinker quotes a leading scientist who also has a clinical practice: “I am incredibly disciplined in the diagnostic classifications in my research, but in my private practice, I'll call a kid a zebra if it will get him the educational services I think he needs.” 

The article has some sobering thoughts on recovery:
Few children ever diagnosed with ASD were said to have actually had and recovered from ASD. Only 21% of children with a lost diagnosis (or less than 3% of all schoolaged CSHCN ever diagnosed with ASD) were said to have lost it due to treatment or maturity. The true rate of recovery may be even smaller if some of these children were incorrectly thought by their parents or doctors to have lost their ASD because they now have well-developed coping skills and other strengths.
The authors appropriately note serious limitations to the study:
The impact of selection biases resulting from sampling, nonresponse, and lack of coverage of non-English speaking households and households without telephones is unknowable, but they are less likely to influence the magnitude of comparisons between matched pairs than absolute estimates of a population prevalence. Still, due to the low response rate, generalizing the results beyond the sample should be done with caution.
The absence of Spanish-only respondents is a serious limitation indeed, since underdiagnosis seems to be a problem among Hispanic families.

More broadly, such a study does not capture the flip side:  people who were incorrectly labeled as not having ASD.  As I write:
Bias can run in the other direction, too. If a school district does not really want to provide services, its psychologists might feel pressure to code behavior in a way that spells “normal.”