Myotonic Dystrophy 1 (DMPK) Genetic Testing (Repeat Expansion)
CPT:
81234
Special Instructions
This assay is not currently available in New York state.
Expected Turnaround Time
2 - 4 weeks
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
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