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Guest blog: Utah, revisited

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Deborah Bilder
25 September 2012

In the 1980s, researchers at the University of California, Los Angeles, and the University of Utah ran an extensive, four-year media campaign across the state of Utah to recruit children with autism, ages 3 to 25, for a study of prevalence in that state.

My colleagues and I decided to revisit the 1980s study to better understand how the changing diagnostic criteria influence prevalence estimates in Utah, independent of these other factors.

The original Utah study provided a good basis for comparison because of its unique scope. Researchers recruited participants by asking practitioners, clinics, schools and social service agencies for referrals, as well as from screening records at residential facilities, group homes and state hospitals. Of the 489 children who were recruited, the researchers diagnosed 241 with autism. 

When we reanalyzed the data collected from that study, we found that the prevalence would have been much higher had the children been evaluated using today’s criteria.

Diagnostic influence

More than half (59 percent) of the 248 children recruited for the study but not originally identified with ‘autistic disorder’ using the Diagnostic and Statistical Manual of Mental Disorders III (DSM-III), meet today’s criteria for an autism spectrum disorder (ASD) as outlined in the DSM-IV-TR.

The results provide direct evidence that changes in diagnostic criteria influence prevalence estimates.

Most (94 percent) of the individuals newly identified as having ASD meet the DSM-IV-TR criteria for ‘full autistic disorder,’ the most restrictive ASD category, suggesting a higher severity of symptoms. (In addition to autistic disorder, the DSM-IV-TR criteria for ASDs include pervasive developmental disorder-not otherwise specified [PDD-NOS] and Asperger syndrome.)

Previous studies comparing the DSM-IV-TR with the DSM-III have found that the modern criteria capture more higher-functioning individuals. Our study found that the DSM-IV-TR guidelines identify more people with lower levels of intellectual ability as well. Those newly identified with ASD using the DSM-IV-TR criteria have a lower intelligence quotient than those diagnosed with autism in the original study.

Although it’s not a primary focus of this study, we did look at the potential impact of the DSM-5, the upcoming version of the diagnostic manual, which is still being revised.

We found that the proposed changes, which include a return to fewer subgroups and a requirement that all three social impairment criteria be met, would exclude only a small number of children from a diagnosis of autism. These are the children who do not have a documented impairment in nonverbal communication.

Given that nearly all the newly identified individuals in this study meet the criteria for full autistic disorder rather than for PDD-NOS or Asperger syndrome, this finding is not surprising. It also cannot be generalized to the current dilemma of whether DSM-5 criteria will exclude high-functioning individuals (such as those with Asperger syndrome).

Deborah Bilder is assistant professor of psychiatry at the University of Utah School of Medicine.

 

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Comments

Name: Paul Whiteley
25 September 2012 - 8:15PM

An interesting post, thanks.

I note that a similar finding was reported at IMFAR 2011 by Rice and colleagues based on DSM-III, DSM-IIIR & DSM-IVTR criteria:

https://imfar.confex.com/imfar/2011/webprogram/Paper8278.html

To quote: "These results indicate that a portion of the increase in identified ASD prevalence over time may be attributed to differences in community identification based on the criteria used to characterize the symptom constellation that makes up the PDDs."

Name: ASD Dad
29 September 2012 - 11:43AM

ASD diagnosis and prevalence often feels like grasping air. The figures are a roller coaster ride which needs urgent clarification. One of the best ways might be to start to combine medical biomarkers with psychological profiles.
I was interested to note this in the above article

"Most (94 percent) of the individuals newly identified as having ASD meet the DSM-IV-TR criteria for ‘full autistic disorder,’ the most restrictive ASD category, suggesting a higher severity of symptoms."

Interestingly the Brugha UK study of Adult ASD (1.1%) actually is suggestive of a higher historical rate primarily because it did not capture ...

"It is likely that autism is more prevalent in some populations that were not sampled in the household survey. For example, people who live in communal care establishments, such as residential homes and nursing homes, and those in other communal establishments, such as prisons, have been found to have a higher prevalence of autism19,20. Secondly, people with learning disabilities (defined by a significant intellectual impairment with onset before adulthood and deficits in skills needed for daily functioning21-23) could not take part in the APMS 2007 because the consent forms, questionnaires and assessments were designed for people with full decision-making capacity. This group has an increased risk of autism; current evidence suggests that the prevalence of autism in adults with learning disabilities is between 7 per cent and 20 per cent24,25, perhaps higher still among those in residential homes26"

..and not addressed in the paper the high ASD mortality recently reported by Professor Bilder and fellow researchers at the University of Utah at

"twenty-nine of these individuals (9.5 %) died by the time of follow up, representing a hazard rate ratio of 9.9 (95 % CI 5.7-17.2) in relation to population controls."

Name: ASD Dad
29 September 2012 - 12:26PM

I also forgot to add in regards to the Brugha study that the methodology employed . May be problematic in trying to identify a group of people defined by social and communication difficulties , language difficulties and co-morbid aspects like anxiety.

Name: ASD Dad
30 September 2012 - 2:13PM

I should also note the co-morbid psychiatric conditions such as schizophrenia, depression / bipolar disorders and substance abuse that may camouflage Adult ASD.

Schizophrenia is particularly interesting to note as Harvard researchers found ..

“19.44% of ASD patients had epilepsy as compared to 2.19% in the overall hospital population (95% confidence interval for difference in percentages 13.58-14.69%),

2.43% of ASD with schizophrenia vs. 0.24% in the hospital population (95% CI 1.89-2.39%),

inflammatory bowel disease (IBD) 0.83% vs. 0.54% (95% CI 0.13-0.43%),

bowel disorders (without IBD) 11.74% vs. 4.5% (95% CI 5.72-6.68%),

CNS/cranial anomalies 12.45% vs. 1.19% (95% CI 9.41-10.38%),

diabetes mellitus type I (DM1) 0.79% vs. 0.34% (95% CI 0.3-0.6%),

muscular dystrophy 0.47% vs 0.05% (95% CI 0.26-0.49%),

sleep disorders 1.12% vs. 0.14% (95% CI 0.79-1.14%).”

Particularly the development of disease moving into adulthood

“Three of the studied comorbidities increased significantly when comparing ages 0-17 vs 18-34 with p<0.001:

chizophrenia (1.43% vs. 8.76%),

diabetes mellitus type I (0.67% vs. 2.08%),

IBD (0.68% vs. 1.99%)”’

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