Fragile X Analysis, Molecular Diagnosis

Fragile X Analysis, Molecular Diagnosis
WSLH Department: Cytogenetics
WSLH Test Code:828
Includes:Determination of CGG repeat expansion in the 5' untranslated region (5' UTR) of FMR1. Initial analysis includes a screening assay which indicates presence of alleles greater than 55 repeats and a sizing assay which provides CGG repeat size up to 200 repeats. PCR analysis (screening or sizing) indicating the presence of an allele greater than 55 repeats is reflexed to methylation-specific PCR for characterization of methylation status.
Methodology:**(CPT Codes: 81243, 81244)** The number of CGG repeats in the 5'-untranslated region (5'-UTR) of the FMR1 gene is determined using triplet repeat-primed PCR followed by size analysis using capillary electrophoresis. The Asuragen, Inc. AmplideX FMR1 assay quantitates CGG repeat lengths up to 200 and identifies normal (5-44 repeats), intermediate (45-54 repeats), pre-mutation (55~200 repeats), and full mutation alleles (reported as >200 repeats) (Monaghan et al. 2013, PMID: 23765048). The presence of size mosaicism can be detected but is not quantifiable. Methylation status is characterized for all pre-mutation and full mutation alleles using methylation specific PCR performed by Prevention Genetics.
Availability:Monday-Friday 7:45 AM - 4:30 PM, Saturday 7:45 AM - 12:00 PM
Turn-around Time:Approximately 14 days. (Reports are issued Monday-Friday 7:45 AM - 4:30 PM)
Recommended Uses:To identify expansions of the CGG repeats in the FMR1 gene in Xq27.3 associated with FMR1-related disorders (fragile X syndrome, fragile X-associated tremor/ataxia syndrome (FXTAS), and FMR1-related primary ovarian insufficiency (POI).
Contraindications: 
Specimen Requirements:6 ml (preferred) - 2 ml (minimum) of peripheral blood in sterile EDTA (purple top) vacuum type tubes.
Collection Kit/Container: 
Patient Preparation: 
Collection Instructions:Draw blood using aseptic techniques into a sterile EDTA vacuum type tube(s). Invert tube(s) to mix. If using larger tubes, draw to full volume to avoid over-treatment with anticoagulant.
Specimen Handling and Transport:Store and transport specimens at room temperature (may transport with coolant during hot, >85 degrees F weather). DO NOT FREEZE. The laboratory must receive specimens within 24-48 hours of collection.
Unacceptable Conditions:Blood must not be frozen or hemolyzed. Plasma and serum are not acceptable.
Requisition Form:Cytogenetics Lab Genetic Diagnosis Form #131
Required Information:Laboratory regulations require the following minimum information to be provided on the requisition form for a specimen to be accepted for testing: Patient name or unique identifier; date and time of collection, patient date of birth and sex, specimen type/site of collection, test request(s), reason for referral, clinician name and UPIN/NPI, and address for reporting results. Please be certain that name/identifier on the form matches that on the specimen label.
Results include:FMR1 CGG expansion detected/not detected. Repeat size of alleles observed.
Limitations:CGG-repeat-expansion full mutations account for >99 percent of cases of fragile X syndrome. Rare mutations in the FMR1 gene unrelated to CGG repeat expansion will not be detected by this assay. Allele drop out and non-detection may occur due to rare sequence variations within the primer regions.
Additional Tests Recommended:The American College of Medical Genetics and Genomics (ACMG) has recommended that array comparative genomic hybridization (aCGH) is used as a first-line test in the evaluation of individuals with multiple congenital anomalies, non-syndromic intellectual and developmental disability, and autism spectrum disorders. This is not required in cases with a family history of documented Fragile X mutation.
Additional Comments: 
Additional Tests Performed: 

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