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Test Code AFXN Friedreich Ataxia, Repeat Expansion Analysis, Varies


Additional Testing Requirements


All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen as this must be a different order number than the prenatal specimen.



Shipping Instructions


Specimen preferred to arrive within 96 hours of collection.



Specimen Required


Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. For instructions for testing patients who have received a bone marrow transplant, call 800-533-1710.

 

Submit only 1 of the following specimens:

 

Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send whole blood specimen in original tube. Do not aliquot.

Specimen Stability Information: Ambient (preferred) 4 days/Refrigerated

 

Prenatal Specimens

Due to its complexity, consultation with the laboratory is required for all prenatal testing; call 800-533-1710 to speak to a genetic counselor. 

 

Specimen Type: Amniotic fluid

Container/Tube: Amniotic fluid container

Specimen Volume: 20 mL

Specimen Stability Information: Refrigerated (preferred)/Ambient

Additional information:

1. A separate culture charge will be assessed under CULAF / Culture for Genetic Testing, Amniotic Fluid.

2. All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.

 

Specimen Type: Chorionic villi

Container/Tube: 15-mL tube containing 15 mL of transport media

Specimen Volume: 20 mg

Specimen Stability Information: Refrigerated

Additional Information:

1. A separate culture charge will be assessed under CULFB / Fibroblast Culture for Biochemical or Molecular Testing. An additional 3 to 4 weeks is required to culture fibroblasts before genetic testing can occur.

2. All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.

 

Acceptable:

Specimen Type: Confluent cultured cells

Container/Tube: T-25 flask

Specimen Volume: 2 Flasks

Collection Instructions: Submit confluent cultured cells from another laboratory.

Specimen Stability Information: Ambient (preferred)/Refrigerated

Additional Information: All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.

 

Specimen Type: Blood spot

Supplies: Card-Blood Spot Collection (Filter Paper) (T493)

Container/Tube:

Preferred: Collection card (Whatman Protein Saver 903 Paper)

Acceptable: Perkin/Elmer 266 filter paper, or Blood Spot Collection Card

Specimen Volume: 5 Blood spots

Collection Instructions:

1. An alternative blood collection option for a patient older than 1 year is a fingerstick. For detailed instructions, see How to Collect Dried Blood Spot Samples.

2. Let blood dry on the filter paper at ambient temperature in a horizontal position for a minimum of 3 hours.

3. Do not expose specimen to heat or direct sunlight.

4. Do not stack wet specimens.

5. Keep specimen dry.

Specimen Stability Information: Ambient (preferred)/Refrigerated

Additional Information:

1. For collection instructions, see Blood Spot Collection Instructions

2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777)

3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800)

4. Due to lower concentration of DNA yielded from blood spots, it is possible that additional specimen may be required to complete testing.


Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Molecular Genetics: Neurology Patient Information

3. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Neurology Specialty Testing Client Test Request (T732)

-Biochemical Genetics Test Request (T798)

Useful For

Molecular confirmation of clinically suspected Friedreich ataxia

Testing Algorithm

For prenatal specimens only:

If amniotic fluid (nonconfluent cultured cells) is received, the amniotic fluid culture will be added at an additional charge.

 

If chorionic villus specimen (nonconfluent cultured cells) is received, the fibroblast culture will be added at an additional charge.

 

For any prenatal specimen that is received, maternal cell contamination studies will be added. A maternal whole blood specimen is required to perform this test.

Method Name

Polymerase Chain Reaction (PCR)

Reporting Name

FXN, Repeat Expansion Analysis

Specimen Type

Varies

Specimen Minimum Volume

Amniotic fluid: 10 mL
Blood: 0.5 mL
Chorionic villi: 5 mg
Blood spots: 5 punches, 3-mm diameter

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Reference Values

FXN

Normal alleles: <34 GAA repeats

Borderline alleles: 34-65 GAA repeats

Expanded alleles: >65 GAA repeats

 

An interpretive report will be provided.

Day(s) Performed

Monday, Wednesday

Report Available

21 to 28 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

81284

81265-Maternal Cell Contamination (if appropriate)

88233-Fibroblast Culture (if appropriate)

88235-Amniotic Fluid Culture (if appropriate)

88240-Cryopreservation (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
AFXN FXN, Repeat Expansion Analysis 21762-0

 

Result ID Test Result Name Result LOINC Value
609752 Result Summary 50397-9
609753 Result 21762-0
609754 Interpretation 69047-9
609755 Reason for Referral 42349-1
609756 Specimen 31208-2
609757 Source 31208-2
609758 Method 85069-3
609759 Disclaimer 62364-5
609760 Released By 18771-6