, a new study suggests.
Researchers, led by Jiamei Zhang, MS, Department of Rehabilitation Medicine, Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China, in a multicenter, prospective cohort study enrolled patients ages 12 to 60 months with GDD from six centers in China from July 2020 through August 2023. Participants underwent trio whole exome sequencing (trio-WES) paired with copy number variation sequencing (CNV-seq).
“To the best of our knowledge, this study represents the largest prospective examination of combined genetic testing methods in a GDD cohort,” the authors reported in JAMA Network Open.
GDD is a common neurodevelopmental disorder, marked by cognitive impairment, and affects about 1% of children, the paper states. Most children with GDD develop intellectual disability (ID) after 5 years of age, with implications for quality of life, their physical abilities, and social functioning. Early and accurate diagnosis followed by appropriately targeted treatment is critical, but lacking. Researchers note that there is lack of consensus among health care professionals on whether genetic testing is necessary.
Genetics are known to play a significant role in pathogenesis of GDD, but definitive biomarkers have been elusive.
Positive Detection Rate of 61%
In this study, the combined use of trio-WES with CNV-seq in children with early-stage GDD resulted in a positive detection rate of 61%, a significant improvement over performing individual tests, “enhancing the positive detection rate by 18%-40%,” the researchers wrote. The combined approach also saves families time and costs, they note, while leading to more comprehensive genetic analysis and fewer missed diagnoses.
The combined approach also addressed the limitations of trio-WES and CNV-seq used alone, the authors wrote. Because of technological constraints, trio-WES may miss 55% of CNV variations, and CNV-seq has a missed diagnosis rate of 3%.
The study included 434 patients with GDD (60% male; average age, 25 months) with diverse degrees of cognitive impairment: mild (23%); moderate (32%); severe (28%); and profound (17%).
Three characteristics were linked with higher likelihood of having genetic variants: Craniofacial abnormalities (odds ratio [OR], 2.27; 95% confidence interval [CI], 1.45-3.56); moderate or severe cognitive impairment (OR, 1.69; 95% CI, 1.05-2.70); and age between 12 and 24 months (OR, 1.57; 95% CI, 1.05-2.35).
Dopaminergic Pathway Promising for Treatment
Researchers also discovered that GDD-related genes were primarily enriched in lysosome, dopaminergic synapse, and lysine degradation pathways. Dopaminergic synapse emerged as a significant pathway linked with GDD.
“In this cohort study, our findings support the correlation between dopaminergic synapse and cognitive impairment, as substantiated by prior research and animal models. Therefore, targeting the dopaminergic pathway holds promise for treating GDD and ID,” the authors wrote.
However, the authors note in the limitations that they used only a subset of 100 patients with GDD to measure dopamine concentration.
“Expanding the sample size and conducting in vivo and in vitro experiments are necessary steps to verify whether dopamine can be targeted for clinical precision medical intervention in patients with GDD,” they wrote.
The authors reported no relevant financial relationships.