Pediatricians might not be aware of guidelines for genetic testing in children with global developmental delay (GDD), even though they often order such tests. This suggests the need for doctors to receive up-to-date training on genetic testing for GDD, especially as new tests are developed.
The study with those findings, “Paediatricians underuse recommended genetic tests in children with global developmental delay,” was published in the journal Pediatrics & Child Health.
GDD is defined as a significant delay in at least two areas of development, including language, motor development, and socialization. GDD can occur in combination with other conditions, like epilepsy and autism spectrum disorder, or it can occur on its own, which is called isolated GDD.
Somewhere between a fifth and half of GDD cases are due to genetic changes, though other factors, like exposure to toxins or infection in the womb, also can cause GDD. When GDD is genetic, understanding the underlying cause can help care providers better predict what will happen in a given case and offer the best treatment possible.
Because of this, numerous organizations — including the American Academy of Pediatrics (AAP), the American Academy of Neurology (AAN) and the American College of Medical Genetics (ACMG) — have issued guidelines for doing genetic tests in GDD cases. Although there is some variation between guidelines, all agree that testing for fragile X syndrome should be a first-line genetic test.
Such tests used to be done with a method called karyotyping, which basically involves visualizing chromosomes to look for abnormalities — in fragile X, (an) irregular X chromosome(s) (depending on whether it’s a male or female). However, in recent years karyotyping has been replaced by a technique called array comparative genomic hybridization (aCGH), which uses specific DNA probes to find changes in chromosomes.
Yet, such guidelines are truly useful only if pediatricians know about them and are following them. Do they, and are they? To find out, a team of Canadian researchers invited all 651 registered pediatricians in Quebec, Canada, to fill out a questionnaire. Of these, 141 returned surveys and had seen patients with GDD.
The majority of participants (93.6%) had used genetic testing for cases of GDD. The three tests used most often were karyotype (92.9%), fragile X testing (87.2%) and fluorescence in situ hybridization (FISH) (68.1%) for specific syndromes. In addition, 35.5% participants reported having used molecular tests to look for specific genetic conditions, such as Rett syndrome.
Almost 64% of the participants had used aCGH at least once and the majority (88.7%) had heard of aCGH.
The researchers also found that pediatricians responding to the survey had little knowledge of the available guidelines; only a third had heard of at least one of the available guidelines, with the AAP guidelines being the most well-known.
When asked what they would do in hypothetical scenarios, many of the pediatricians reported they would take actions not recommended by the guidelines. For example, only about a fifth of respondents said they would order genetic testing for isolated GDD, even though all the guidelines recommend karyotype and/or aCGH and fragile X testing in all cases of GDD.
These results suggest pediatricians need to be made aware of the available genetic tests, as well as how and when these tests should be used.
“As new and more complex genetic tests are developed, we suggest that up-to-date training about the use of genetic tests for children with GDD be integrated at all levels of training, from pediatrics residency curriculum to continuous medical education activities, to ensure that pediatricians in practice are knowledgeable about indications for testing, pretest counselling, and appropriate interpretation and management of results,” researchers concluded.