Corrections to the blogosphere, the consensus, and the world

Saturday, May 16, 2009

Autism Screening

This Saturday's All in the Mind program was on people calling for universal screening at or around birth for autism.

Early screening for autism is crazy for so many reasons....

a) The instability of diagnosis:
As Michelle Dawson points out on the Autism Crisis blog,
"Turner and Stone (2007) were looking at the stability of autism diagnosis at around age two years (mean age of 29 months). They carefully used various combinations within what is considered the gold-standard diagnosis: ADOS, ADI-R, and clinical judgment. And they found that early diagnosis, in their sample of 48 originally autistic children, was very unstable.

By age four (mean age of 53 months), only 53% of children originally given the specific diagnosis of autism retained this specific diagnosis, while only 68% were still on the autistic spectrum. The rest were not. That is a 32% rate of "recovery." Only 40% of children originally diagnosed with PDD-NOS at age two still had an autistic spectrum diagnosis by age four. That would be a 60% rate of "recovery."

The children whose age two diagnoses were unstable were largely still regarded as having difficulties, a finding that echoes Dr Fein's work, but they no longer could be diagnosed as autistic.

Turner and Stone (2007) attempted to associate instability of diagnosis (what is being called "recovery") with interventions received, but no association was found. They report:

All children in the sample received speech therapy, and the majority received additional interventions. There were no significant differences between the Stable and Change groups for the amount of speech therapy, t(46) = .30, p = .77, behavioral therapy, t(46) = .78, p = .44, occupational therapy, t(46) = 1.90, p = .06, special education, t(46) = 1.96, p = .06, or regular preschool, t(46) = .13, p = .90. Of the 6 children who received an average of 20 or more hours of intervention per week, 5 were in the Stable group and 1 was in the Change group.

In other words, few of the 48 originally autistic children in this study received what would be considered "intensive" intervention, and the majority of those who did kept their autism diagnosis.

In contrast, Turner and Stone (2007) found that diagnostic instability was related to earliness of diagnosis: the earlier the diagnosis, the more unstable it was.

The authors go on to discuss what may underlie the diagnostic instability they found while using the best available diagnostic standards. In fact there are many possible explanations. One point they do underline, however, is that given their findings,

...extreme caution must be taken when interpreting intervention findings that suggest ‘cures.’

And of course that would include intervention findings that suggest "recovery." This may be all the more so when diagnosis, and therefore intervention, is very early."

To be sure, there was a suggestion in the program that the universal screening wouldn't use the old-fashioned and exploded testing that had been refuted by evidence, but instead some new and untested undefined combination of different viewpoints that there was no test data on at all, but I'm not sure that that helps.

b) The stigmatising effect
It's also true that much autism is diagnosed only after regression around the age of three, and it wouldn't seem that even an improved observational system would help there. And if the genetic testing did pick up this group, that too has its downside; as it is, parents have a chance to bond with their kids before the autism kicks in, whereas if there was a genetic test they'd be on notice that their child was defective from birth - which would have to affect the natural bonding process.

On the other hand, pushing for universal screening would be rational for certain interest groups, for several other reasons;
i) if you wanted to prove that there was an epidemic of autism (given that greatly increasing the numbers screened would, given the false positive rate, greatly increase the number diagnosed with autism)
2) if you wanted to prove that early intervention worked (in that half of the children diagnosed would emerge from the diagnosis whatever treatment was given, putting a solid floor under your results)

I suspect, too, that 'early intervention' is simply code for ABA. Which would certainly be one reason for pushing screening; if you could get all diagnosed children receiving early intervention treatment, and that treatment was ABA, that's about one child in a hundred at a cost of $40,000 per year each.

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