SAN FRANCISCO, Oct. 13 (UPI) -- Many practitioners with autistic patients consider one of their biggest challenges to be keeping up with what one of them refers to as "the changing face" of the disorder.
"It's been truly trying for the best diagnosticians to be able to classify our children over time," said Dr. Rafael Castro, a Boston neuropsychologist.
"There have been instances in which they have been grouped with kids who had childhood schizophrenia," he added. "Most recently, they've added other diagnoses, such as the Asperger's disorder and PDDNOS (pervasive developmental disorder not otherwise specified), and it does reflect the variation that we can find in the presentation of the symptomatology."
In 14 years, between 1980 and 1994, the official diagnostic manual of mental illnesses expanded the definition of "pervasive developmental disorders" -- as the range of conditions on the autistic spectrum are called in scientific circles -- from two categories to five.
Ranging from debilitating impairment to near-normal functioning in most settings, these include the severe classic autism, the much milder Asperger's syndrome and an intersection of the two, termed PDDNOS.
In addition, the group also comprises the rare but severe Rett's disorder, which affects primarily girls, and "childhood disintegrative disorder." Both of these involve a regression that wipes out earlier developmental milestones in social, language and/or cognitive skills.
Overall, an estimated 425,000 children under age 18 and 100,000 younger than 5 have a pervasive developmental disorder, according to Dr. Deborah Hirtz of the National Institute of Neurological Disorders and Stroke, a component of the National Institutes of Health, in Bethesda, Md.
She approximates one to three out of 1,000 children have autism, and three to six of 1,000 have combined pervasive developmental disorders.
The ubiquitous one in 166 figure popping up on and off the Internet is the simplified form of six in 1,000, the highest rate studies suggest for the most liberally inclusive category of autism, which encompasses the mildest forms of the condition, scientists say.
No actual head count has been taken of Americans with autism spectrum disorders, and no one knows exactly how many children are affected, the Department of Health and Human Services acknowledges.
The figures cited are derived by assuming a 1-in-166 prevalence and applying it to the 4 million children born in the United States each year. Of these, then, approximately 24,000 would have an autistic disorder.
Presuming this proportion has stayed steady for the past two decades, the Centers for Disease Control and Prevention in Atlanta calculates the total number of autistic children through age 20 should hover somewhere around 480,000.
That sum would be lower if the mildest cases were omitted, or if, as mercury-in-vaccines critics contend, the percentages have been soaring along with the expansion of the childhood immunization program.
Or they might be higher, if the base rate has been undervalued.
CDC Director Dr. Julie Gerberding stresses the one in 166 figure was drawn from a small sample and has been used as a stopgap until studies currently under way in a number of states and other research present a truer measure of the problem.
Findings made public in May 2006 from two of the ongoing national studies -- the first ever based on parents' reports of children's autism diagnosis -- suggested between 5.5 and 5.7 per 1,000 (or one in 182 to one in 175) youngsters ages 4 to 17, or at least 300,000, were identified with the disorder as of 2003-2004.
However, because neither survey distinguished among the various types of autism, the results provided no hint to how many cases were of the less severe forms. In addition, because both studies covered the same period, they gave no indication how these rates compare to those of the past.
Thus, the findings offered little resolution to the continuing debate over the direction of the patterns in prevalence.
"We're just learning about the subtleties that can be early signs of autism, we're learning about the importance of early detection, and we're learning about the importance of early treatment, but we have a long way to go before we really understand the scope and magnitude of this problem in our country and what the trends really mean," Gerberding said.
Next: Coexisting conditions further muddy autism count.
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