Affymetrix’s CytoScan Dx Assay, which can detect chromosomal variations linked to developmental delays or intellectual disabilities in children, has been granted marketing approval by the Food and Drug Administration (FDA) today. “This new tool may help in the identification of possible causes of a child’s developmental delay or intellectual disability, allowing health care providers and parents to intervene with appropriate care and support for the child,” said Dr. Alberto Gutierrez, director of the Office of In Vitro Diagnostics and Radiological Health at the FDA. An intellectual disability, which affects between one and three percent of the population, is a condition diagnosed before age 18 that includes below-average intellectual function and a lack of skills necessary for daily living.

Requiring an infant’s blood sample, the genotyping assay is meant to aid diagnosis of an intellectual disability. The FDA’s review of the CytoScan Dx Assay included evaluation of the test’s ability to accurately detect numerous chromosomal variations of different types, sizes, and genome locations. Such "genotyping" is the process of determining a person’s genetic constitution — the entirety of their genes, the sequences of code inherited from each parent that include, in some cases, sequence changes due to environmental damage or biological errors. Many intellectual and developmental disabilities, such as Down syndrome and DiGeorge syndrome, are associated with chromosomal variations, according to the National Institutes of Health. One of the most common forms of genetic variation, as described by Affymetrix, is a single-nucleotide polymorphism, or SNP, which is a variation in a single position in a DNA sequence. Another common aberration is copy number variations, or CNV, which is a variation in the number of copies of a segment of the DNA. In its evaluation, the FDA also compared the assay to several commonly used test methods, including karyotyping and FISH chromosomal tests and found that in 960 blood specimens, CytoScan had a better ability to detect certain chromosomal abnormalities.

“The FDA’s review of the test provides clinical laboratories with information about the expected performance of the device and the quality of the results,” Gutierrez noted. A primary FDA expectation is that test results be performed and interpreted by properly certified health care professionals. Additionally, the agency noted the device should not be used for prenatal testing or screening, pre-implantation testing or screening, population screening, or for the detection of aberrations occurring after birth, such as cancer. Last year, GenomeWeb reported that Doug Farrell, the company’s director of investor relations, said gaining FDA clearance would be unlikely to "change the trajectory of the [CytoScan] business dramatically" though it would give the company an advantage in winning new customers.