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A B C D E F G H I J K L M N O P Q

Test Identifier Information

 
Registration CodeFRGX
Method

Fluorescently tagged PCR fragments from the FMR1 CGG repeat region at Xq27.3 are accurately sized on the ABI3130xl Genetic Analyser. Triplet repeat primed PCR (TP-PCR) may be employed in some cases to detect large CGG expansions.

Diagnostic Use / Indications

The classic fragile X syndrome phenotype is male mental retardation to varying degrees, mild dysmorphic (abnormal-appearing) features, and enlargement of the testes in adults. Female heterozygotes may also be affected, depending on the pattern of X-inactivation in the brain.

External Price$215.73(Exclusive of GST)
  

Specimen Collection

 
Patient Specimen4.0mL EDTA,
Paediatric Specimen0.5 mL - 1 mL EDTA blood
Sample Delivery to LabAmbient
  

CHLabs Laboratory

 
DepartmentBiochemistry - Molecular Pathology
Contact Details Email Email
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Contact Phone Number03 3640 548
Test Availability9am to 5pm, Monday to Friday
Turnaround TimeWithin 4 weeks
Reference Interval

FMR1 CGG repeat numbers are reported:

Normal: <50 repeats
Intermediate: 50-58 repeats
Premutation: 59-approximately 200 repeats, unmethylated
Full mutation: Greater than approximately 200 repeats, methylated

Accurate sizing for alleles >90 repeats is not possible. See Interpretation.

 

Interpretation

CGG repeats of normal, intermediate and low premutation size are amplified in the standard PCR. Normal males are identified by the presence of an allele with less than 58 CGG repeats. Premutations up to about 90 repeats are detectable. Females heterozygous for two normal alleles are also identified however about one-third of normal females are homozygous and are indistinguishable from fragile-X carriers in the standard PCR assay. These females, as well as the minority of samples which fail to amplify are re-analysed by triplet repeat primed PCR (TP-PCR) which reliably detects expanded CGG repeats in the 100 to >1000 repeat range but does not determine
repeat number.

Uncertainty of Measurement

The PCR assay has an uncertainty of measurement of one repeat unit within the normal and intermediate size ranges, verified by testing the NIST fragile X Standard Reference Material PN2399.

Additional Information

This genetic analysis requires nucleated cells. Please don’t centrifuge or freeze the EDTA blood tube.

If storing blood tube prior to delivery please refrigerate at 4 degrees (transport still at ambient temperature).

Delphic Number Test Number5138

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