Clinicians increasingly rely on genetic tests as a diagnostic tool for developmental disabilities (DD). A technical brief issued by the Agency for Healthcare Research and Quality (AHRQ), “Genetic Testing for Developmental Disabilities, Intellectual Disability, and Autism Spectrum Disorder,” sheds some clarity on the clinical applications of these tests and which ones are available for use in the United States.

“DDs are a group of conditions associated with functional impairment in physical, learning, language, or behavior areas,” AHRQ’s brief explained. DDs, as categorized by the Centers for Disease Control and Prevention, may include: autism spectrum disorder (ASD), hearing loss, vision impairment, learning disability, attention deficit/hyperactivity disorder, cerebral palsy, intellectual disability (ID), Tourette syndrome, and other conditions.

DDs affect about 15% of children aged 3 to 17 years in the United States.

AHRQ drew from numerous sources to conduct its research, seeking a variety of perspectives from nine key informants or experts in the healthcare field. It combed through 15 years of studies on the clinical use of genetic tests, and relied on the National Center for Biotechnology Information’s Genetic Testing Registry (GTR) as a key source for identifying genetic tests.

All genetic tests in the United States available for clinical use fall into one of two categories: a laboratory- developed test (LDT) or a test approved or cleared by the Food and Drug Administration (FDA).

The GTR database search revealed that 63 laboratories in 29 U.S. states offer 672 LDT genetic tests for developmental disabilities. All of these tests were registered as “clinical tests” with “how to order” information.

AHRQ identified one FDA-cleared, commercial genetic test that didn’t fall into the same category as the GTR tests.

“Common genetic testing methods used include array comparative genomic hybridization, microarray, DNA sequencing (the Sanger method or next-generation sequencing), and polymerase chain reaction,” AHRQ indicated in its brief. Compared with other DD categories, mental retardation or ID tests seemed to be the tests most frequently used.

Not all states house a lab that provides these types of genetic tests—and some might offer a variety of tests for the same condition, such as ID, AHRQ noted. “The impact of the laboratories’ geographic distribution on genetic tests’ availability is unclear, because patients may receive testing services from laboratories in other states,” according to the technical brief.

AHRQ’s analysis of the GTR data didn’t make any predictions about future use of genetic tests, and which ones might play the biggest role in DD care.

“We did not identify any data based analysis that predicted the trend of genetic technologies for DD diagnosis or screening. However, our interview of the Key Informants suggested that the whole exome or genome sequencing may be increasingly used in the context of DD care as the cost for these tests continue to drop,” according to the technical brief.