Fragile X Syndrome, Carrier

Synonyms

Fragile X testing

Test Details

Turnaround Time

8 - 14 days

In some cases, additional time may be required for confirmatory or reflex tests.

Use

Carrier screening for fragile X syndrome.

Special Instructions

To test fetal specimens, including cordblood, order test code 481718, Fragile X Syndrome, Fetal Analysis

Test Includes

This test includes the following gene: FMR1

Limitations

Technologies used do not detect germline mosaicism and do not rule out the presence of large chromosomal aberrations including rearrangements and gene fusions, or variants in regions or genes not included in this test, or possible inter/intragenic interactions between variants, or repeat expansions. Variant classification and/or interpretation may change over time if more information becomes available. False positive or false negative results may occur for reasons that include: rare genetic variants, sex chromosome abnormalities, pseudogene interference, blood transfusions, bone marrow transplantation, somatic or tissue-specific mosaicism, mislabeled samples, or erroneous representation of family relationships. This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

Polymerase chain reaction (PCR) followed by capillary electrophoresis, with reflex to AGG interruption analysis and methylation PCR analysis for positive samples.

References

Hunter JE, Berry-Kravis H, et al., FMR1 Disorders. 1998 Jun16 (Updated 2019 Nov 21). In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews®[Internet]. PMID: 20301558

Spector E, Behlmann A, Kronquist K, et al. Laboratory testing for fragile X, 2021 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG). Genet Med 23, 799 (2021). PMID: 33795824

Specimen Requirements

Information on collection, storage, and volume

Specimen

Whole blood or PurFlock buccal swab kit or Oragene Dx 500 saliva kit

Volume

8.5 mL whole blood or PurFlock buccal swab kit or Oragene Dx saliva kit

Minimum Volume

3 mL whole blood or PurFlock buccal swab kit or Oragene Dx saliva kit

Container

Yellow-top (ACD-A) or lavender-top (EDTA) or pink-top (EDTA) or tan-top (EDTA) tubes or PurFlock buccal swab kit or Oragene Dx 500 saliva collection kit

Storage Instructions

Maintain specimen at room temperature or refrigerate at 4┬░C. Do not freeze.

Causes for Rejection

Frozen or hemolyzed specimen; quantity not sufficient for analysis; improper container

Collection

Standard phlebotomy. Follow PurFlock buccal swab kit or Oragene Dx 500 saliva kit collection instructions. Do not eat, drink, smoke, or chew gum 30 min prior to collection.