Test Catalog

Test Id : AFXN

Friedreich Ataxia, Repeat Expansion Analysis, Varies

Useful For
Suggests clinical disorders or settings where the test may be helpful

Molecular confirmation of clinically suspected Friedreich ataxia

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

This test assesses for GAA (trinucleotide repeat expansions within the FXN gene to confirm a molecular diagnosis of Friedreich ataxia.

Reflex Tests
Lists tests that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial tests.

Test Id Reporting Name Available Separately Always Performed
CULFB Fibroblast Culture for Genetic Test Yes No
CULAF Amniotic Fluid Culture/Genetic Test Yes No
MATCC Maternal Cell Contamination, B Yes No

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Polymerase Chain Reaction (PCR)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

FXN, Repeat Expansion Analysis

Aliases
Lists additional common names for a test, as an aid in searching

FRDA

FRDA1

FXN

FARR

Friedreich Ataxia with Retained Reflexes

Ataxia

Frataxin

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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.

Specimen Type
Describes the specimen type validated for testing

Varies

Shipping Instructions

Specimen preferred to arrive within 96 hours of collection.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

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

 

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)/Refrigerated

 

Due to its complexity, prenatal testing will not be accepted without approval from the laboratory. Call 800-533-1710 for prenatal testing consultation. Prenatal specimens can be sent Monday through Thursday and must be received by 5 p.m. CST on Friday in order to be processed appropriately. 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: Amniotic fluid

Container/Tube: Amniotic fluid container

Specimen Volume: 20 mL

Specimen Stability Information: Refrigerated (preferred)/Ambient

 

Specimen Type: Chorionic villi

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

Specimen Volume: 20 mg

Specimen Stability Information: Refrigerated

 

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

 

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 (formerly Ahlstrom 226) 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 of age is a fingerstick. See Dried Blood Spot Collection Tutorial for how to collect blood spots via fingerstick: https://vimeo.com/508490782 .

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.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

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)

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

Amniotic fluid: 10 mL

Blood: 0.5 mL

Chorionic Villi: 5 mg

Blood Spots: 5 punches, 3-mm diameter

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Varies Varies (preferred)

Useful For
Suggests clinical disorders or settings where the test may be helpful

Molecular confirmation of clinically suspected Friedreich ataxia

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

This test assesses for GAA (trinucleotide repeat expansions within the FXN gene to confirm a molecular diagnosis of Friedreich ataxia.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Friedreich ataxia (FA) is one of the most commonly inherited ataxias and is characterized by progressive gait and limb ataxia, dysarthria, dysphagia, and sensory loss. The phenotypic spectrum includes nonneurologic manifestations, particularly cardiomyopathy and diabetes mellitus. Onset typically occurs between the ages of 10 to 16 years; however, late-onset and early-onset variants have been reported. FA is autosomal recessively inherited. The majority of affected individuals (96%) have homozygous GAA trinucleotide repeat expansions in intron 1 of FXN. The remaining affected individuals have a heterozygous GAA trinucleotide repeat expansion and another pathogenic FXN variant detectable by sequencing or deletion and duplication analysis. Correlation exists between the size of the GAA repeat and disease onset and severity, with larger alleles associated with earlier onset and more severe disease presentation. GAA expansions may demonstrate instability during meiosis and mitosis. The GAA repeat size may expand or contract during transmission to offspring and GAA repeat size may vary in different tissues. The GAA trinucleotide repeat is polymorphic in the general population, with the number of nondisease-associated repeats ranging from 5 to 33. Repeats of 66, or greater, are fully penetrant disease-associated alleles; however, the majority of affected individuals have repeat sizes in the 600 to 1200 repeat range. Repeat sizes of 34 to 65 fall within a borderline range. Borderline alleles are of unclear significance and may be associated with clinical symptoms of FA and/or a risk for expansion to a full penetrance allele when transmitted to offspring.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

FXN

Normal alleles: <34 GAA repeats

Borderline alleles: 34-65 GAA repeats

Expanded alleles: >65 GAA repeats

 

An interpretive report will be provided.

Interpretation
Provides information to assist in interpretation of the test results

An interpretive report will be provided.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

For familial testing, it is important to first document the molecular etiology of disease in an affected family member to confirm that a repeat expansion is the underlying mechanism of disease in the family. Specifically, this assay will not detect nonrepeat expansion variants (eg, sequence variants, deletions, and duplications).

 

It is strongly recommended that patients undergoing genetic testing receive genetic counseling.

 

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data, such as frataxin concentrations (see FFRWB / Friedreich Ataxia, Frataxin, Quantitative, Blood and FFRBS / Friedreich Ataxia, Frataxin, Quantitative, Blood Spot). Errors in test interpretation may occur if the provided information is inaccurate or incomplete.

 

Rare variants (ie, polymorphisms) may exist, such as intron 1 deletions, which could lead to false-negative results. If GAA-repeat expansion results do not match clinical findings, additional testing should be considered.

 

Due to somatic mosaicism, GAA repeat-sizes in peripheral blood specimens may not reflect GAA repeat-sizes in other tissues (eg, central nervous system).

 

Bone marrow transplants from allogenic donors will interfere with testing. Call Mayo Clinic Laboratories at 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Campuzano V, Montermini L, Molto M, et al: Friedreich’s ataxia: autosomal recessive disease caused by an intronic GAA triplet repeat expansion. Science. 1996 Mar;271(5254):1423-1427

2. Delatycki M, Bidichandani S: Friedreich ataxia-pathogenesis and implications for therapies. Neurobiol Dis. 2019 Dec;132:104606

3. Corben L, Lynch D, Pandolfo M, et al: Consensus clinical management guidelines for Friedreich ataxia. Orphanet J Rare Dis. 2014 Nov 30;9:184

4. Sharma R, De Biase I, Gomez M, et al: Friedreich ataxia in carriers of unstable borderline GAA triplet-repeat alleles. Ann Neurol. 2004 Dec;56(6):898-901

5. Montermini L, Richter A, Morgan K, et al: Phenotypic variability in Friedreich ataxia: role of the associated GAA triplet repeat expansion. Ann Neurol. 1997 May;41(5):675-682

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

A polymerase chain reaction-based assay is used to amplify across the region of FXN containing GAA repeats.(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday, Wednesday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

8 to 16 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

Whole Blood: 2 weeks (if available) Extracted DNA: 3 months

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

81284

81265-Maternal Cell Contamination (if appropriate)

88233- Fibroblast Culture (if appropriate)

88235-Amniotic Fluid Culture (if appropriate)

88240-Cryopreservation (if appropriate)

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
AFXN FXN, Repeat Expansion Analysis 21762-0
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
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

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Create a PDF

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports