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HelpEpic Code LAB848 Huntington Disease, Molecular Analysis, Varies
Additional Codes
Mayo Code: HAD
Performing Laboratory
Mayo Clinic Laboratories in Rochester
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
Specimen Type
VariesShipping Instructions
Specimen preferred to arrive within 96 hours of collection.
Necessary Information
Molecular Genetics: Neurology Patient Information or a recent clinical note is required. Testing cannot proceed without this information.
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 whole blood specimen in original tube. Do not aliquot.
Special Instructions
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Ambient (preferred) | ||
| Frozen | |||
| Refrigerated | |||
Reject Due To
All specimens will be evaluated by Mayo Clinic Laboratories for test suitability.Day(s) Performed
Wednesday
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.
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).
Cautions
For predictive testing, it is important to first document the presence of a CAG-repeat amplification in the HTT gene in an affected family member to confirm that molecular expansion is the underlying mechanism of disease in the family.
It is strongly recommended that patients undergoing predictive testing receive genetic counseling both prior to testing and after results are available.
Predictive testing of an asymptomatic child is not recommended.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in the interpretation of results may occur if information given is inaccurate or incomplete.
Interpretation
An interpretive report will be provided.
Reporting Name
Huntington Disease AnalysisMethod Name
Polymerase Chain Reaction (PCR)
Method Description
A polymerase chain reaction-based assay is utilized to detect expansions of a CAG trinucleotide tract in exon 1 of the HTT gene.(Unpublished Mayo method)
CPT Code Information
81271-HTT (huntingtin) (eg, Huntington disease) gene analysis; 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 |
Report Available
7 to 11 days upon receipt of sufficient clinical information for testingTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.Clinical Reference
1. ACMG/ASHG statement. Laboratory guidelines for Huntington disease genetic testing. The American College of Medical Genetics/American Society of Human Genetics Huntington Disease Genetic Testing Working Group. Am J Hum Genet. 1998 May;62(5):1243-1247
2. Potter NT, Spector EB, Prior TW: Technical standards and guidelines for Huntington disease testing. Genet Med. 2004;6(1):61-65. doi: 10.1097/01.gim.0000106165.74751.15
Forms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.