Fragile X, PCR and Southern Blot Analysis

CPT: 81243; 81244
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Test Details

Synonyms

  • FRAXA

Use

Diagnostic testing for:

• Unexplained intellectual disabilities, developmental delay, or autism

• Women with primary ovarian insufficiency or failure, premature menopause, or infertility associated with elevated FSH levels before the age of 40 with no known cause

• Individuals with late onset intention tremor and/or cerebellar ataxia of unknown origin

Methodology

Polymerase chain reaction (PCR) followed by capillary electrophoresis and Southern blot analysis performed on all samples at the same time

Additional Information

Fragile X syndrome is the leading cause of inherited intellectual disability, affecting approximately 1 in 4,000 males and 1 in 8,000 females. It is found in all ethnic groups, and can occur in families with no history of intellectual disability. Women may decide to have testing to find out if they are carriers, and therefore are at risk of having a child with fragile X syndrome. The carrier frequency in women is approximately 1 in 260. Fragile X test is commonly used for individuals at higher risk, including those that may be symptomatic or have a family history suggestive of fragile X syndrome.

Specimen Requirements

Specimen

Whole blood

Volume

10 mL

Container

Lavender-top (EDTA) tube or yellow-top (ACD) tube

Storage Instructions

Room temperature

Causes for Rejection

Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; unlabeled or mislabeled specimen

Clinical Information

References

American College of Obstetricians and Gynecologists Committee on Genetics. Committee Opinion No. 469: Carrier screening for fragile X syndrome. Obstet Gynecol. 2010;116(4):1008-10.20859177
Hagerman PJ, Hagerman RJ. The fragile X premutation: A maturing perspective. Am J Hum Genet. 2004 May;74(5):805-816.15052536
Jacquemont S, Hagerman RJ, Leehey MA, et al. Penetrance of the fragile X-associated tremor/ataxia syndrome in a premutation carrier population. JAMA. 2004 Jan 28;291(4): 460-469.14747503

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