Friedreich Ataxia Genetic Testing (Trinucleotide Repeat Expansion)

TEST: 620077
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CPT: 81284
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Special Instructions

This assay is not currently available in New York state.

Expected Turnaround Time

14 - 28 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Whole blood; oral swab or extracted DNA (from blood or oral swab only)

Volume

Whole blood: 4 mL; oral swab: 3 swabs; or extracted DNA: contact MNG Genetic Services 844-664-8378 (844-MNGTEST)

Minimum Volume

Whole blood: 2 mL; oral swab: 1 swab; or extracted DNA: contact MNG Genetic Services 844-664-8378 (844-MNGTEST)

Container

Whole blood: lavender-top (EDTA) tube; oral swab: OCD-100 DNA Genotek; or extracted DNA: contact MNG Genetic Services 844-664-8378 (844-MNGTEST)

Collection

Whole blood: standard phlebotomy; oral swab: follow kit instructions; or extracted DNA: contact MNG Genetic Services 844-664-8378 (844-MNGTEST)

Storage Instructions

Maintain specimen at room temperature or refrigerate at 4°C. Do not freeze.

Stability Requirements

• Room temperature: whole blood: 14 days; swab: 60 days

• Refrigerated: whole blood: 30 days; swab: 60 days

• Frozen: do not freeze

Causes for Rejection

Frozen or hemolyzed specimen; quantity not sufficient for analysis; improper container

Test Details

Use

Diagnostic testing

Limitations

False positive or false negative results may occur for reasons that include insufficient information available about rare genetic variants, allele dropout, blood transfusions, bone marrow transplantation, somatic or tissue-specific mosaicism or mislabeled samples. Maximum reportable size of repeat expansion testing: ATN1: 110 repeats; ATXN1: 150 repeats (repeats greater than 40 in the ATXN1 gene cannot be assessed for CAT interruptions); ATXN2: 150 repeats; ATXN3: 120 repeats; ATXN7: 125 repeats; ATXN8/ATXN8OS: 150 repeats; ATXN10: 70 repeats; C9orf72: 65 repeats; CACNA1A: 145 repeats; CNBP: 373 base pairs (approximately 75 repeats); DMPK: 150 repeats; FXN: 1300 repeats; HTT: 100 repeats; JPH3: 100 repeats; NOP56: 65 repeats; PPP2R2B: 150 repeats; TBP: 120 repeats. Repeat sizes greater than the maximum reportable range are reported as greater than the largest reportable repeat size.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

Repeat-primed PCR and fragment length analysis to identify number of nucleotide repeats

For Providers

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CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2021, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf