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Friedreich's Ataxia

FRDA

Test Codes

BAYLOR 6031. Testing requires pathology approval prior to collection.

Department

Send Outs

Instructions

This test is not included in the Beaumont Laboratory testing formulary, however, the Laboratory can facilitate specimen collection.

• This test requires pathology review. Contact the Send Outs Laboratory at 248-551-9045 before ordering this test.
• Testing requires the ordering physician to complete forms for the independent clinical laboratory performing the testing.
• This test will be billed to the patient's insurance. If not covered by insurance, the patient is responsible for the full cost of testing.
• Specimens received without the appropriate forms and information will not be shipped.
• Once approved, order test as a Miscellaneous Send Out (XMISC). 

Specimen Collection Criteria

Collect (Adults): Two Lavender-top EDTA tubes, after obtaining necessary pathology approval.
Also acceptable (Children/Infants): One Lavender-top EDTA tube, after obtaining necessary pathology approval.

Physician Office/Draw Specimen Preparation

Do not centrifuge. Maintain whole blood specimens at room temperature (20-26°C or 68-78.8°F).

Preparation for Courier Transport

Transport: Whole blood in EDTA tubes, at room temperature (20-26°C or 68-78.8°F) (Minimum: 3.0 mL Adult) (Minimum: 2.0 mL Children).

Rejection Criteria

Specimens received without prior laboratory notification and review.

Specimens not collected and processed as indicated.

In-Lab Processing

Do not centrifuge. Maintain whole blood specimens at room temperature (20-26°C or 68-78.8°F).

Transport: Whole blood in EDTA tubes, at room temperature (20-26°C or 68-78.8°F) (Minimum: 3.0 mL Adult) (Minimum: 2.0 mL Children). 

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 7 days
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Baylor Genetics, DNA Diagnostic Laboratory, Houston, TX.

Performed

Results available within 21 days.

Reference Range

The mutation responsible for FRDA resides in a novel gene (X25) which maps to 9q13 and is characterized by expansion of an unstable GAA trinucleotide repeat. Normal individuals have 7-34 repeats, while FRDA patients have expansions of 120 repeats or greater. To date, alleles between the normal and abnormal ranges have not been observed. Due to limitations in test methodology alleles with 35 to 60 repeats may not be distinguished from those under 35 repeats. Correlations of length of the repeat with age of onset of disease is not precise enough to be used clinically.

Test Methodology

Southern Blot, Polymerase Chain Reaction (PCR).

Interpretation

By report.

Clinical Utility

This assay aids in the confirmation of diagnosis in a symptomatic individual. It is also used for carrier or predictive testing of asymptomatic individuals with a positive family history for FRDA. (Molecular analysis of the affected relative or both of the carrier parents is required.) This test is also used for prenatal testing for high-risk families. (Molecular analysis of the affected relative or both of the carrier parents is required.)

Note: The Baylor College of Medicine, DNA Diagnostic Laboratory recommends that genetic and/or psychological counseling be made available to all individuals considering having confirmatory, carrier or predictive testing for FRDA.

Clinical Disease

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder with an incidence of approximately 1 in 50,000. FRDA is characterized by progressive gait and limb ataxia, lack of tendon reflexes in the legs, loss of position sense, dysarthria, and pyramidal weakness of the legs. Hypertrophic cardiomyopathy is found in almost all patients and diabetes mellitus is seen in 10% of the patients. The age of onset is usually around puberty, almost always before 25 years with a slow progression of the disease.

CPT Codes

81284

Contacts

Last Updated

10/3/2023