FDA Approves Asuragen’s Genetic Test to Diagnose Fragile X Syndrome

Rare Daily Staff

The U.S. Food and Drug Administration cleared for marketing Asurgen’s AmplideX Fragile X test, the first test to detect a genetic condition known as Fragile X syndrome, the most common known cause of inherited developmental delay and intellectual disability.

The test is also indicated for use in screening asymptomatic carriers at-risk for having children with fragile X syndrome.

The test was cleared based on evaluation of data from specimens collected during two trials conducted at three clinical sites, which demonstrated 95 percent diagnostic accuracy of the test.

Fragile X syndrome (FXS) affects an estimated 1 in 4000 males and 1 in 8000 females in the United States. The X-linked disorder is caused by changes in the FMR1 gene located on the X chromosome.

A segment of the DNA in the gene, known as a CGG trinucleotide repeat, is repeated in excess on the X chromosome in people with Fragile X. While some repetition of the CGG repeat is normal, a high number of repeats may indicate potential health risks.

The AmplideX Fragile X Dx and Carrier Screen Kit uses blood specimens from patients to measure the number of repeats of the CGG segment in the FMR1 gene. The test can determine whether a patient has a number of CGG repeats that is considered either normal, intermediate, permutation, or full mutation.

Individuals with a full mutation typically have FXS, which is associated with developmental delays, learning disabilities, social and behavioral issues, intellectual disabilities, and autism spectrum disorder. Women with a premutation have an increased risk of having a child with FXS as compared to women without a premutation. The number of women who have the Fragile X premutation is believed to be approximately 1 in 150 women. Men with a premutation will pass the premutation to their daughters only. Individuals with normal or intermediate levels of repeated CGG segments are currently thought to be asymptomatic for FXS or other fragile X-associated disorders.

In addition to aiding in the diagnosis of FXS and for carrier testing, this test can be used as an aid in the diagnosis of fragile X-associated disorders, including fragile X-associated tremor/ataxia syndrome, which is a movement and cognitive disorder that typically occurs in adults over age 50, and fragile X-associated primary ovarian insufficiency, a condition that is characterized by reduced function of the ovaries. Asurgen’s test is not intended for use in fetal diagnostic testing, the screening of eggs obtained for in-vitro fertilization prior to implantation, or stand‐alone diagnoses of FXS. 

“Enabling better access to testing to predict and diagnose these cases significantly improves our ability to make a difference in these patients’ lives by eliminating the diagnostic odyssey that many families experience and allowing more accurate genetic counseling,” said Elizabeth Berry-Kravis, co-investigator of the study and co-director of the molecular diagnostics section of the genetics laboratory and professor of pediatrics and neurological sciences at Rush University Medical Center.

Photo: Elizabeth Berry-Kravis, co-investigator of the study and co-director of the molecular diagnostics section of the genetics laboratory and professor of pediatrics and neurological sciences at Rush University Medical Center