Myotonic Dystrophy Mutation Type 1
DMPK
Test Codes
BAYLOR: 6041, Testing requires pathology approval prior to collection.
Department
Send Outs
Instructions
This test is not included in the Beaumont Laboratory testing formulary, however, the Laboratory can facilitate specimen collection.
- This test requires pathology review. Contact the Send Outs Laboratory at 248-551-9045 before ordering this test.
- Testing requires the ordering physician to complete forms for the independent clinical laboratory performing the testing.
- This test will be billed to the patient's insurance. If not covered by insurance, the patient is responsible for the full cost of testing.
- Specimens received without the appropriate forms and information will not be shipped.
- Once approved, order test as a Miscellaneous Send Out (XMISC).
Specimen Collection Criteria
Collect (Adults): Two Lavender-top EDTA tubes, after obtaining necessary pathology approval.
Also acceptable (Children/Infants): One Lavender-top EDTA tube, after obtaining necessary pathology approval.
Physician Office/Draw Specimen Preparation
Do not centrifuge. Maintain whole blood specimens at room temperature (20-26°C or 68-78.8°F).
Preparation for Courier Transport
Transport: Whole blood in EDTA tubes, at room temperature (20-26°C or 68-78.8°F) (Minimum: 3.0 mL Adult) (Minimum: 2.0 mL Child).
Rejection Criteria
Specimens received without prior laboratory notification and review.
Specimens not collected and processed as indicated.
In-Lab Processing
Do not centrifuge. Maintain whole blood specimens at room temperature (20-26°C or 68-78.8°F).
Transport: Whole blood in EDTA tubes, at room temperature (20-26°C or 68-78.8°F).
Storage
Specimen Stability for Testing:
Room Temperature (20-26°C or 68-78.8°F): 7 days
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable
Specimen Storage in Department Prior to Disposal:
Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.
Laboratory
Sent to Baylor Genetics, DNA Diagnostic Laboratory, Houston, TX.
Performed
Results available within 21 days.
Reference Range
By report.
Test Methodology
Polymerase Chain Reacation (PCR) Amplification, Southern Blot with Densitometry.
Interpretation
The mutation causing myotonic dystrophy has been identified as an unstable expanded (CTG)n repeat in the 3' untranslated region of the myotonin protein kinase gene on chromosome 19. Usually, normal individuals have between five and 35 repeats, mildly affected patients have 50-150 repeats, and adult onset (classical) patients have 100-1000 repeats. Transmission of mutant alleles to successive generations is generally accompanied by increases in the number of CTG repeats plus earlier onset of myotonic dystrophy and an increase in the clinical severity. Congenital cases of myotonic dystrophy usually have >1000 copies of the repeat and in all but rare cases involve maternal transmission of the mutant allele.
Clinical Utility
This assay aids in the diagnosis of myotonia (progressive muscle weakness and wasting) and for individuals suspected of having Myotonic Dystrophy.
CPT Codes
81234
Contacts
Send Outs Laboratory – RO
248-551-9045
Name: Send Outs Laboratory – RO
Location:
Phone: 248-551-9045
Last Updated
10/3/2023
Microtainer® and Vacutainer® are registered trademarks of Becton, Dickinson and Company.
UroVysion® is a registered trademark of Abbott Laboratories. ThinPrep® is a registered trademark of Hologic, Incorporated.