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Epic Code LAB848 Huntington Disease, Molecular Analysis, Varies

Important Note

Presymptomatic testing requires documented informed consent and both neurological and psychological evaluation. Please contact Genetic Services for more information (616-391-2700).

Order as Reference Miscellaneous #LAB848; indicate complete test name when ordering.

Additional Codes

Mayo Code: HAD


Reporting Name

Huntington Disease Analysis

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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).

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


Shipping 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


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.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Ambient (preferred)

Reject Due To

All specimens will be evaluated by Mayo Clinic Laboratories for test suitability.

Day(s) Performed


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.


An interpretive report will be provided.


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.

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

Method 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)

Report Available

7 to 11 days upon receipt of sufficient clinical information for testing

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 US Food and Drug Administration.

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


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.