Test Summary
Fragile X syndrome (FXS OMIM # 300624) is the most common inherited mental retardation syndrome, affecting approximately 1:4000 males and approximately 1:8000 females. The disease is caused by the expansion of a trinucleotide CGG repeat in the 5'-untranslated (UTR) region of the FMR1 gene. Methylation of the expanded CGG tract leads to silencing of expression of the FMR1 gene. The American College of Medical Genetics defines a normal repeat length as between 5 and 44. Intermediate alleles of between 45-54 repeats almost never expand to full mutations in a single meiosis. Premutation alleles are defined as 55-200 CGG. Premutation alleles of less than 90 repeats have a variable risk for expansion to full mutations whereas larger premutation alleles almost always expand when inherited through a female. Full mutation alleles are defined as >200 repeats. FXS in an X-linked dominant disease. The test is used to detect the presence of expanded alleles in the FMR1 gene and to distinguish normal homozygous females from full mutation carriers.
Aliases
Specimen Collection
Special Instructions
N/A
Preferred Specimen
4 mL whole blood collected in an EDTA (lavender-top) or ACD (yellow-top) or sodium heparin (green-top) tube
Minimum Volume
3 mL
Instructions
Normal phlebotomy procedure. Specimen stability is crucial. Store and ship room temperature immediately. Do not freeze.
Patient Preparation
N/A
Storage
N/A
Transport Temperature
Room temperature
Specimen Stability
- Room temperature: 8 days
- Refrigerated: 8 days
- Frozen: Do not freeze
Limitations
This analysis evaluates only the size of the FMR1 CGG repeat and cannot detect other possible chromosomal or DNA abnormalities. This assay cannot rule out the possibility of Fragile X syndrome caused by any other type of mutation in the FMR1 gene. In addition, this assay may not detect a FMR1 CGG expansion that presents with low-level mosaicism (this means that the expansion is present in only some cells not all cells). DNA analysis can predict the occurrence of Fragile X syndrome, but not the severity of the condition.
Other Acceptable Specimens
no other acceptable specimens
Unacceptable Specimens
Extensive hemolysis observed; sample received frozen
Order Code
FRAGLX
EPIC (Premier) Code
LAB5040
Includes
If Fragile X, PCR result is not Normal, or Gray zone, then Fragile X Methylation Analysis will be performed at an additional charge (CPT codes(s): 81244)
CPT Code
Billing Code
CPT Statement
Methodology
Polymerase Chain Reaction (PCR) with Detection by Capillary Electrophoresis
FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. The FDA has determined that such clearance or approval is not necessary. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Physician Attestation of Informed Consent
This germline genetic test requires physician attestation that patient consent has been received if ordering medical facility is located in AK, DE, FL, GA, IA, MA, MN, NV, NJ, NY, OR, SD or VT or test is performed in MA.
Testing Laboratory
Quest Diagnostics Nichols Institute
33608 Ortega Highway
San Juan Capistrano CA, 92675
Department
Reference Testing
Reference Range
See Laboratory Report
Setup Schedule / Expected Turnaround Time
Daily; Report available: 10 days(4 days for PCR and 6 days additional if reflex required)
Specimen Collection
Special Instructions
N/A
Preferred Specimen
4 mL whole blood collected in an EDTA (lavender-top) or ACD (yellow-top) or sodium heparin (green-top) tube
Minimum Volume
3 mL
Instructions
Normal phlebotomy procedure. Specimen stability is crucial. Store and ship room temperature immediately. Do not freeze.
Patient Preparation
N/A
Storage
N/A
Transport Temperature
Room temperature
Specimen Stability
- Room temperature: 8 days
- Refrigerated: 8 days
- Frozen: Do not freeze
Limitations
This analysis evaluates only the size of the FMR1 CGG repeat and cannot detect other possible chromosomal or DNA abnormalities. This assay cannot rule out the possibility of Fragile X syndrome caused by any other type of mutation in the FMR1 gene. In addition, this assay may not detect a FMR1 CGG expansion that presents with low-level mosaicism (this means that the expansion is present in only some cells not all cells). DNA analysis can predict the occurrence of Fragile X syndrome, but not the severity of the condition.
Other Acceptable Specimens
no other acceptable specimens
Unacceptable Specimens
Extensive hemolysis observed; sample received frozen
Billing
CPT Code
Billing Code
CPT Statement
Result Information
Methodology
Polymerase Chain Reaction (PCR) with Detection by Capillary Electrophoresis
Testing Laboratory
N/A
Reference Range
See Laboratory Report
Setup Schedule / Expected Turnaround Time
Daily; Report available: 10 days(4 days for PCR and 6 days additional if reflex required)
