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HelpTest ID: HAD Huntington Disease, Molecular Analysis
Useful For
Molecular confirmation of clinically suspected cases of Huntington disease (HD)
Presymptomatic testing for individuals with a family history of HD and a documented expansion in the HTT gene
Special Instructions
Method Name
Polymerase Chain Reaction (PCR)
Reporting Name
Huntington Disease AnalysisSpecimen Type
VariesShipping Instructions
Specimen preferred to arrive within 96 hours of draw.
Specimen Required
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.
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 specimen in original tube.
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Ambient (preferred) | |
| Frozen | ||
| Refrigerated | ||
Clinical Information
Huntington disease (HD) is an autosomal dominant progressive neurodegenerative disorder caused by a CAG repeat expansion in the HTT gene. HD is associated with cognitive impairment leading to dementia and a wide range of neuropsychiatric problems including apathy, depression, anxiety, and other behavioral disturbances. Additionally, affected individuals typically develop extrapyramidal symptoms (eg, dystonia, dysarthria, chorea, gait disturbance, postural instability, oculomotor dysfunction).
Reference Values
Normal alleles: <27 CAG repeats
Intermediate alleles: 27-35 CAG repeats
Reduced penetrance: 36-39 CAG repeats
Full penetrance: >39 CAG repeats
An interpretive report will be provided.
Interpretation
An interpretive report will be provided.
Clinical Reference
1. American College of Medical Genetics/American Society of Human Genetics Huntington Disease Genetic Testing Working Group: Laboratory guidelines for Huntington disease genetic testing. Am J Hum Genet 1998;62:1243-1247
2. Potter NT, Spector EB, Prior TW: Technical standards and guidelines for Huntington disease testing. Genet Med 2004;6:61-65
Day(s) and Time(s) Performed
Tuesday, 10 am
Specimens received Tuesday through Saturday will be processed for the run starting on following Tuesday. Specimens received on Monday will be set up a week from the following Tuesday.
Analytic Time
4 days upon receipt of sufficient clinical information for testing.CPT Code Information
81401-HTT (huntingtin) (eg, Huntington disease), evaluation to detect abnormal (eg, expanded) alleles
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| HAD | Huntington Disease Analysis | 21763-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 52885 | Result Summary | 50397-9 |
| 52886 | Result | 53782-9 |
| 52887 | Interpretation | 69047-9 |
| 52888 | Reason for Referral | 42349-1 |
| 52889 | Specimen | 31208-2 |
| 52890 | Source | 31208-2 |
| 52891 | Released By | 18771-6 |
Test Classification
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 U.S. Food and Drug Administration.Forms
2. Molecular Genetics: Neurology Patient Information in Special Instructions
3. If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)
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