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Friedreich Ataxia Genetic Testing (Trinucleotide Repeat Expansion)

CPT: 81284
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Special Instructions

Test orders should now be placed through Labcorp using test code 620077
 


Genes Assessed

FXN

Specimen Requirements


Specimen

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


Volume

Whole blood: 4 ml
Oral swab: 3 swabs
Extracted DNA: Contact MNG Genetic Services 844-664-8378 (844-MNGTEST) 


Minimum Volume

Whole blood: 2 ml
Oral swab: 1 swab
Extracted DNA: Contact MNG Genetic Services 844-664-8378 (844-MNGTEST)


Container

Whole blood: Lavender-top (EDTA) 
Oral swab: OCD-100 DNA Genotek
Extracted DNA: Contact MNG Genetic Services 844-664-8378 (844-MNGTEST)


Collection

Whole blood: standard phlebotomy. 
Oral swab: follow kit instructions
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

Friedreich ataxia is a genetic condition that affects the nervous system and causes movement problems.


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
.


Recommended MNG Kits

SINGLE Blood Genetic Testing, Buccal Swab Genetic Testing


LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
620077 Friedreich Ataxia Repeat Exp 21762-0 620078 FRDARE Genetic Test Result 21762-0
620077 Friedreich Ataxia Repeat Exp 21762-0 620079 FRDARE Genetic Test Int. 50397-9
620077 Friedreich Ataxia Repeat Exp 21762-0 630829 PDF 85063-0