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Huntington Disease
Clinical Genetic Test
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offered by
Johns Hopkins Genomics DNA Diagnostic Laboratory
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GTR Test Accession: Help GTR000500905.4
INHERITED DISEASENERVOUS SYSTEM
Last updated in GTR: 2024-08-30
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Last annual review date for the lab: 2024-08-30 LinkOut
At a Glance
Test purpose: Help
Diagnosis; Pre-symptomatic
Conditions (1): Help
Huntington disease
Genes (1): Help
HTT (4p16.3)
Methods (1): Help
Molecular Genetics - Targeted variant analysis: Trinucleotide repeat by PCR or Southern Blot
Target population: Help
Individuals with known or highly suspected Huntington Disease; relatives of …
Clinical validity: Help
Of patients meeting clinical diagnostic criteria for Huntington Disease, 98-99% …
Clinical utility: Help
Not provided
Ordering Information
Offered by: Help
Johns Hopkins Genomics DNA Diagnostic Laboratory
View lab's website
View lab's test page
Test short name: Help
HD
Specimen Source: Help
Who can order: Help
  • Genetic Counselor
  • Health Care Provider
Test Order Code: Help
Huntington Disease
View other test codes
CPT codes: Help
**AMA CPT codes notice

Copyright: 2023 American Medical Association. All rights reserved.

Lab contact: Help
Hannah Shultz-Lutwyche, BS, Genetic Counselor Assistant
hlutwyc1@jhmi.edu
410-955-0483
Sumathi Rachamadugu, MS, MSc, CGC, Genetic Counselor
sracham1@jhmi.edu
443-927-3089
Contact Policy: Help
Laboratory can only accept contact from health care providers. Patients/families are encouraged to discuss genetic testing options with their health care provider.
How to Order: Help
Submit sample with completed requisition form
Order URL
Test service: Help
Clinical Testing/Confirmation of Mutations Identified Previously
Confirmation of research findings
Test development: Help
Test developed by laboratory but exempt from FDA oversight (eg. NYS CLEP approved, offered within a hospital or clinic)
Informed consent required: Help
Yes
Pre-test genetic counseling required: Help
Decline to answer
Post-test genetic counseling required: Help
Decline to answer
Recommended fields not provided:
Test strategy
Conditions Help
Total conditions: 1
Condition/Phenotype Identifier
Test Targets
Genes Help
Total genes: 1
Gene Associated Condition Germline or Somatic Allele (Lab-provided) Variant in NCBI
Methodology
Total methods: 1
Method Category Help
Test method Help
Instrument *
Targeted variant analysis
Trinucleotide repeat by PCR or Southern Blot
* Instrument: Not provided
Clinical Information
Test purpose: Help
Diagnosis; Pre-symptomatic
Clinical validity: Help
Of patients meeting clinical diagnostic criteria for Huntington Disease, 98-99% will have an expanded CAG repeat in exon 1 of the HTT gene. Reduced penetrance (60% by age 65 and 70% by age 75) has been identified in individuals with expansions from 36 to 39 CAG repeats.
View citations (3)
  • Huntington disease without CAG expansion: phenocopies or errors in assignment?. Andrew SE, et al. Am J Hum Genet. 1994;54(5):852-63. PMID: 8178825.
  • Patients with features similar to Huntington's disease, without CAG expansion in huntingtin. Rosenblatt A, et al. Neurology. 1998;51(1):215-20. doi:10.1212/wnl.51.1.215. PMID: 9674805.
  • Quarrell et al. (2007) J Med Genet. 44 e68 (http://jmedgenet.com/cgi/content/full/44/3/e68)
Target population: Help
Individuals with known or highly suspected Huntington Disease; relatives of a proband with an HTT variant.
Variant Interpretation:
Are family members with defined clinical status recruited to assess significance of VUS without charge? Help
Decline to answer.

Will the lab re-contact the ordering physician if variant interpretation changes? Help
Decline to answer.
Recommended fields not provided:
Clinical utility, What is the protocol for interpreting a variation as a VUS?, Is research allowed on the sample after clinical testing is complete?, Sample negative report, Sample positive report
Technical Information
Availability: Help
Tests performed
Entire test performed in-house
Analytical Validity: Help
+/- 1 CAG repeat up to 40; +/- 2 CAG repeats 41-60; and, +/- 3 CAG repeats when >60 repeats.
Assay limitations: Help
May not detect repeat sizes greater than 101. Analysis parameters are not designed to detect mosaicism.
Proficiency testing (PT):
Is proficiency testing performed for this test? Help
Yes

Method used for proficiency testing: Help
Formal PT program

PT Provider: Help
American College of Physicians - Medical Laboratory Evaluation, ACP MLE
Recommended fields not provided:
Test Confirmation, Citations to support assay limitations, Description of internal test validation method, Citations for Analytical validity, Description of PT method, Major CAP category, CAP category, CAP test list
Regulatory Approval
FDA Review: Help
Category: FDA exercises enforcement discretion
Additional Information

IMPORTANT NOTE: NIH does not independently verify information submitted to GTR; it relies on submitters to provide information that is accurate and not misleading. NIH makes no endorsements of tests or laboratories listed in GTR. GTR is not a substitute for medical advice. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.