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Test Code FRAGX DNA Fragile X DNA

Important Note

As of 6/15/2017, Fragile X DNA Analysis will no longer include reflex testing to estimate repeat size and methylation status for FMR1 gene full expansion mutations.

After this date, the Seattle Children's Molecular Genetics Laboratory will report FMR1 full expansion mutations as >200 CGG repeats (full mutation).  In addition, methylation testing for FMR1 full expansion mutations will no longer be performed by our laboratory, but may be sent out if indicated. See Clinical Utility section for more information. We will continue to report estimated CGG repeat size for normal, intermediate, and premutation FMR1 alleles.


Providers and hospital staff may contact our Laboratory Genetic Counselors (206-987-5400 or with questions.

Clinical System Name

Fragile X DNA Analysis Request





Molecular (DNA) testing to determine the number of CGG repeats in the FMR1 gene.


The test is indicated for:
1. Evaluation of male and female patients with mental retardation, developmental delay and autism.
2. Evaluation of women with premature ovarian failure.
3. Evaluation of older adult males with gait ataxia or intention tremor.
4. Carrier testing for women in a family with history of fragile X syndrome or undiagnosed intellectual disability.

Sample Requirements

Specimen: Whole blood, cord blood

Container(s): Lavender/EDTA, Yellow/ACD A or B

Preferred Vol: 3 mL

Minimum Vol: 1 mL


Specimen: Extracted DNA

Minimum: 5µg

Note: DNA concentration minimum 100 µg/mL; 260/280 ratio 1.70-2.00


Specimen: Cultured cells

Acceptable:  Fibroblasts

Container(s): T-25 flasks

Preferred Vol: 2 flasks

Processing Instructions

Reject due to: n/a

Spin: No

Aliquot: No

Temp: Refrigerate

Storage location: Molecular Genetics box in CPA refrigerator #2


Off-site collection: Refrigerate blood samples until ready to ship.  Transport all sample types at room temperature via overnight shipping.


Specimen Type Temperature Time
Cultured cells Room temp 3 days
Whole blood, extracted DNA Room temp 3-5 days
Whole blood, extracted DNA Refrigerated 7 days
Extracted DNA Frozen ok


Note: Whole blood samples > 7days may be submitted to be assessed by our lab for acceptability for testing.


STAT Performed TAT
Contact lab Monday - Friday 2-3 weeks


Performing Laboratory

Seattle Children's Laboratory


Department:  Molecular Genetics Laboratory

Phone: 206-987-3872


Lab Client Services: 206-987-2617


Lab Genetic Counselor:

Reference Range

Interpretive report will be provided


Method: PCR 

CPT Codes

81243 (updated 11/2/16 by jnaray)

Special Instructions

Links to: FMR1-Related Disorders- GeneReviews


Molecular Genetics

Clinical Utility

FMR1-related disorders include fragile X syndrome, FMR1-related premature ovarian failure (POF), and fragile X-associated tremor/ataxia syndrome (FXTAS). These disorders are due to a repetitive sequence of DNA (CGG repeat) that leads to an expansion of the FMR1 gene. A normal FMR1 gene has approximately 5-44 CGG repeats. Approximately 55-200 repeats are considered premutations and >200 CGG repeats is a full mutation and causes fragile X syndrome. An estimated 1 in 4000 males are affected with fragile X syndrome. Features include developmental delay, learning disabilities, attention deficit, speech delay, gross and fine motor delay, and autistic like behavior. Many females are unaffected carriers of the full expansion, however, females can exhibit symptoms as well. Female carriers of a premutation can have FMR1-related premature ovarian failure. Male premutation carriers can develop FXTAS, characterized by white matter lesions on MRI causing intention tremor or gait ataxia.


More than 99% of individuals with Fragile X syndrome have a loss-of-function variant of FMR1 caused by an increased number of CGG trinucleotide repeats (typically a full mutation, >200 repeats) accompanied by aberrant methylation of FMR1 (FMR1-Related  Disorders - GeneReviews).  The clinical utility of reporting the estimated number of CGG repeats for a full expansion mutation has not been demonstrated for individuals expressing symptoms of Fragile X syndrome.  In addition, the data suggest that the vast majority of FMR1 alleles >200 repeats are fully methylated.  Methylation studies may be sent out upon provider request if the result does not fit the patient's phenotype. 


As of 11/1/16, Fragile X E (FMR2) repeat analysis is no longer available at our laboratory. The SCH Laboratory Test Utilization Management Team has determined that this test has demonstrated a very low yield in the absence of family history of an FMR2 repeat expansion and there is no evidence-based clinical utility for this test.