Fragile X Carrier Screening

This test is designed to detect individuals at risk of transmitting Fragile X related FMR1 gene 5'UTR CGG repeat expansions. Fragile X syndrome is one of the most common forms of inherited intellectual disability. Fragile X syndrome is an X-linked disorder that affects both males and females, but males are usually more severely affected. In addition to developmental delay and intellectual disability, individuals with Fragile X syndrome often have behavioral issues, autism spectrum disorder, and characteristic facial features. In 99% of affected individuals, Fragile X syndrome (MIM 300624) is caused by expansion of the CGG repeat sequence in the 5%u2019UTR of the FMR1 gene (NM_002024) to greater than 200 repeats. This repeat expansion causes hypermethylation of the FMR1 gene, resulting in silencing of FMR1 gene expression. The interpretation of Fragile X test results is based on the number of CGG repeats detected, using the following ranges: <45 repeats is Negative, 45-54 repeats is the Intermediate range, 55-200 repeats is a Premutation, and >200 repeats is a Full Mutation. Individuals with <55 repeats are at low risk for having a child with Fragile X syndrome; however, intermediate alleles may expand into the premutation range in future generations. Fragile X expansions are transmitted from the mother; therefore, females with repeat numbers in the premutation range (55-200 repeats) are at risk of having a child with Fragile X syndrome. Additionally, females in the premutation range may have fragile X-associated primary ovarian insufficiency (MIM 300623) resulting in menopause before the age of 40. Males, and some females, in the premutation range may develop fragile X-associated tremor/ataxia syndrome (MIM 311360), a late onset disorder characterized by tremor, ataxia, and gradual cognitive decline. This test is intended for pre/post-conception carrier screening and is not intended for diagnostic testing.




300624 311360 300623


81243 x 1


Test Code

Additional Test Codes
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Turnaround Time
Typically within 2 weeks from receipt of a sample in the laboratory

Non-Prenatal Specimens
Whole blood: purple-top (EDTA) tube, minimum of 3 ml 2. Genomic DNA: a minimum of 3 ug (at a concentration of at least 30 ng/ul)

Ship all specimen types at room temperature by overnight courier. Do not freeze. For more details and to download the required forms, please visit our shipping page.

The American Medical Association (AMA) Current Procedural Terminology (CPT) codes published by HNL Lab Medicine are guidelines and are intended for informational purposes only. CPT coding is the exclusive responsibility of the billing entity. HNL Lab Medicine strongly recommends confirmation of CPT codes with third-party payors and/or the AMA. We assume no responsibility for billing errors due to reliance upon CPT codes provided by HNL Lab Medicine.