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Saturday, November 11, 2017

Narrowing the Diagnostic Gap: Autism Over 30 Years

From Healio - Infectious Diseases in Children
via the Kennedy Krieger Institute

January, 2017

Susan E. Levy
“The drastic changes in the diagnostic criteria since the 1980s have fueled this reported increase in ASD prevalence,” Susan E. Levy, M.D., MPH, a developmental pediatrician at Children’s Hospital of Philadelphia and Chair of the AAP Autism Subcommittee, said in an interview with Infectious Diseases in Children.

“The current diagnostic criteria include children with different ranges of ability in categories that would not have been considered in 1980.”

She added, “For instance, the ‘infantile autism’ category that researchers focused on in 1980 was reserved for the profoundly impaired, who probably also exhibited severe intellectual disabilities and behavior problems, and thus included severe autism; diagnostic criteria in the 2000s not only included children with severe autism and intellectual disabilities, but also those with Asperger’s syndrome and the now defunct PDDNOS category.”

Although epidemiological studies over the past decade have not conclusively ruled out a ‘true increase’ in the incidence of ASD, neither do they support one; instead, the rise in ASD numbers appears to be associated more with increased parental awareness and improved early diagnosis by pediatricians.

Pediatricians on the Front Lines

Early diagnosis of ASD can be exceedingly challenging during primary care visits because, unlike other conditions that may rely on laboratory tests the pediatrician must instead make a diagnosis based on the presence — or lack thereof — of a pattern of symptoms.

“The earlier a child is identified with ASD, the earlier services and treatment can begin,” Christensen said in an interview. “Therefore, to help improve early identification of ASD, in 2007 the AAP recommended that all children should be screened specifically for ASD during regular well-child visits at 18 and 24 months of age.”

Additional screening might be warranted if a child is at high risk for ASD, for example, if they have an older sibling affected by autism or if parents note behaviors that could be associated with ASD. Although parental observations and concerns are often essential to a timely ASD diagnosis, recent research demonstrates that pediatricians occasionally fail to take these concerns seriously, much to the detriment of their patients.

In a study published in The Journal of Pediatrics, among children diagnosed with autism vs. intellectual disabilities and developmental delays, Zuckerman and colleagues found that pediatricians were 14% less likely to take a proactive approach when parents expressed concerns about autism.

“Children who are diagnosed earlier and receive early intervention quickly perform better in all developmental areas,” Levy said. “Pediatricians should be routinely asking parents if they have any questions regarding their child’s development or behavior. It is essential that pediatricians and families work together with other providers to screen for autism, act on concerns expressed by parents and obtain referrals for further evaluations.”

Striking the Root

More so than other childhood conditions, the search for potential causes of ASD has been plagued by red herrings as parent groups attempt to link ASD to specific ‘controllable’ environmental factors; pediatricians are still living in the shadow of the famously debunked 1998 research of Andrew Wakefield linking autism to measles-mumps-rubella vaccines.

Although researchers continue to investigate a variety of environmental factors, in recent years, research has shown genetic predisposition to be the leading risk factor for ASD.

“Children who have a sibling with ASD are at a higher risk of also having ASD, and ASD tends to occur more often in people who have certain genetic or chromosomal conditions, such as fragile X syndrome or tuberous sclerosis,” Christensen said.

Additionally, in a recent study published in JAMA Psychiatry, Colvert and colleagues determined that genetic heritability of ASD was high compared with other risk factors; in their analysis of 258 twins, researchers estimated that 56-95% of the autism effect had a genetic origin.

“What has become clear is that there are a wide range of gene abnormalities that we now know are causing problems in the autism spectrum,” Lipkin said. “Our hope is that by better understanding these gene abnormalities, clinicians will be able to make improvements in the health and well-being of children with ASD through medical interventions.”

Researchers have not yet identified a single gene that can be held responsible for ASD development; however, investigations into its root cause continue with research investigating the possibility of a multiple gene involvement, a latent susceptibility to ASD, problems during pregnancy, as well as environmental factors including metabolic imbalance and chemical exposure.

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