Last year, the American Psychological Association issued new guidelines for the diagnosis of autism spectrum disorder. But new research from Columbia University School of Nursing in New York, NY, suggests that these guidelines could leave thousands of children who have developmental delays without autism diagnosis, meaning they will miss out on social services, educational support and medical benefits.

The study findings were recently published in the Journal of Autism and Developmental Disorders.

According to the Centers for Disease Control and Prevention (CDC), approximately 1 in 88 children in the US have been diagnosed with autism spectrum disorder (ASD).

For the diagnosis of psychiatric conditions, the American Psychological Association (APA) provide a tool called the Diagnostic and Statistical Manual of Mental Disorders (DSM).

Until last year, health care professionals had been using the fourth edition of a manual called the DSM-IV-TR to diagnose ASD.

This manual included three specific subgroups that were under the definition of ASD. These were autistic disorder (AD), Asperger's disorder and pervasive development disorder-not otherwise specified (PDD-NOS).

However, the APA introduced a revised fifth manual for ASD diagnosis in May 2013 called DSM-5. This manual has limited the range of criteria for ASD diagnosis and completely eliminated the three subgroups included in the old manual.

A new category has also been added to the the DSM-5 manual - social communication disorder (SCD). This category aims to diagnose individuals with impairments in verbal and nonverbal communication who do not have any other characteristics linked to autism.

The APA state that some individuals who would have been diagnosed with PDD-NOS under the old manual would fall under the SCD category using the new manual.

Decrease in ASD diagnosis under new guidelines

To determine how the new guidelines impact ASD diagnosis compared with the old guidelines, Kristine M. Kulage, director of the Office of Scholarship and Research Development at Columbia Nursing, and colleagues reviewed 418 studies looking at autism diagnosis, of which 14 met inclusion criteria.

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Researchers say that under the new DSM-5 manual, autism diagnosis has reduced by more than one third, compared with the number of autism cases that would have been diagnosed under the old guidelines.

From this, the researchers found that under the new DSM-5 manual, there were 31% fewer ASD diagnoses, compared with the number of ASD cases that would have been diagnosed using the old DSM-IV-TR manual.

There was a 22% decrease in AD diagnosis and a 70% decrease in PDD-NOS diagnosis under the DSM-5 manual, compared with what there would have been under the DSM-IV-TR manual.

Furthermore, the investigators found that some individuals who failed to meet the criteria for ASD diagnosis under the new DSM-5 manual also failed to meet criteria for SCD.

The researchers say they did find a decrease in diagnosis for Asperger's disorder using the DSM-5 manual, but they note that the reduction was not statistically significant.

According to Kulage, the team's findings are worrying for children with developmental delays.

She says:

"This study raises a concern that a medical provider diagnosing a child under the new guidelines won't find the child to be on the autism spectrum, when the same child under the old criteria might have been diagnosed with ASD.

We are potentially going to lose diagnosis and treatment for some of the most vulnerable kids who have developmental delays. In many instances, children require a diagnosis of ASD to receive medical benefits, educational support and social services."

Medical News Today recently reported on another study, published in the Journal of the American Academy of Child and Adolescent Psychiatry, that came across similar results.

In this study, researchers found that children who had been identified as having ASD by a health care or education professional were more likely to meet criteria in the DSM-5 manual, compared with the DSM-IV-TR manual. However, they were less likely to be diagnosed with ASD.