• Test Code:
    1620
  • Department:
  • Test Synonyms:
    HDHuntington’s ChoreaHTT
  • CPT Code(s):
    81401*****New Code as of 1/1/2019*****81274
Background:

Huntington Disease (HD) is an inexorably progressive, generally adult onset disorder, characterized by mood and personality changes, clumsiness, chorea, and cognitive decline.  HD is an autosomal dominant disorder caused by the expansion in size of a polymorphic CAG trinucleotide repeat located at the 5'-end of the HTT (also known as HD or IT15) gene.  This gene has been mapped to chromosome 4p16.3.
 
The mean age of adult onset HD is 35 to 44 years with death occurring approximately 15 to 18 years after the onset of symptoms.  Individuals with 36 to 40 CAG repeats may or may not develop Huntington disease, while people with more than 40 repeats almost always develop the disorder.  Individuals with juvenile onset have HD symptoms prior to the age of 20 years and have CAG repeats greater than 60.

Reason for Referral:
The Huntington Disease assay is clinically indicated for the evaluation of:

  • Symptomatic patients with a suspected diagnosis of HD.
  • Presymptomatic patients with a family history of HD and therefore at risk to have inherited a mutant HD allele.

Methodology:

 

Mutation analysis by Triplet Repeat PCR to identify the number of CAG trinucleotide repeats responsible for Huntington disease.

Interpretation:
# of CTG Repeats Interpretation
10-26 No clinical phenotype
27-35 Indeterminate
36-39 Mutant Allele.  Indeterminate clinical phenotype.  Symptoms may not appear in patient's lifetime.
≥40 Clinically affected or likely to become symptomatic in the future.

Specimen Requirements:

  • Blood: 6.0 mL in an EDTA (purple-top) or ACD (yellow-top) tube
  • DNA: 40ng at a minimum of 20ng/µL (DNA must be extracted in a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by the CAP and/or CMS)
A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES.  Please include detailed clinical information,  including ethnicity, clinical history, and family history.

An ordering physician statement must also accompany all requests. For questions please contact Client Services at (855) 535-1522.

Test Performed (Days):

Weekly

Turn Around Time:

14-21 Days

Shipment Sensitivity Requirements:

Package and ship specimen to remain cold, but not frozen.  Ship via overnight express, using the FedEx priority overnight label provided.  Contact Client Services for shipping kits and instructions at (855) 535-1522.

References:

  1. Mohamed Jama, Alison Millson, Christine E. Miller, and Elaine Lyon.  Triplet Repeat Primed PCR Simplifies Testing for Huntington Disease.  The Journal of Molecular Diagnostics, vol. 15, No. 2, March 2013.

Additional Info:

Testing is diagnostic for normal/presymptomatic/disease states. Extensive experience with affected individuals and their families has indicated that it is mandatory for individuals requesting presymptomatic testing to participate in an approved multidisciplinary Huntington disease testing protocol.  Please contact Client Services at (855) 535-1522 prior to drawing samples.

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