Ordering Recommendation

Diagnostic confirmation for Huntington disease (HD) in a symptomatic individual. Presymptomatic testing for adults with a family history of HD.

Mnemonic
HD
Methodology

Polymerase Chain Reaction/Fragment Analysis

Performed

Varies

Reported

7-10 days after receipt of fully completed HD consent form

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).

Specimen Preparation

Transport 5 mL whole blood. (Min: 3 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions
Remarks

A completed HD specific consent form, signed by the patient (or legal guardian) and physician, is required for all specimens. Testing for patients under the age of 18 years or fetal specimens is not offered. Presymptomatic patients are strongly encouraged to be tested through a counseling program approved by the Huntington Disease Society of America at (800) 345-4372. Call Genetics Processing with additional questions at 800-242-2787 ext 3301.

Stability

Ambient: 72 hours; Refrigerated: 1 week; Frozen: 1 month

Reference Interval

Negative: This individual has two normal alleles; and therefore, is neither a carrier nor will be affected with Huntington disease.

Interpretive Data

Background Information for Huntington Disease (HD) Mutation by PCR:
Characteristics:
Neurodegenerative disorder causing progressive cognitive, motor, and psychiatric disturbances typically beginning at 35-44 years of age
(Although, 5 percent are affected as juveniles and 25 percent affected after age 50).
Incidence:
1 in 15,000.
Inheritance:
Autosomal dominant.
Cause:
Expanded number of CAG repeats in the HD gene (27-35 repeats-unaffected, intermediate; 36-39 repeats-reduced penetrance; 40+ repeats-affected, full penetrance).
Clinical Sensitivity and Specificity:
99 percent.
Methodology:
Chimeric PCR followed by size analysis using capillary electrophoresis.
Analytical Sensitivity and Specificity:
99 percent.
Limitations:
Other neurodegenerative disorders will not be detected. Rare, previously unreported variants may interfere with PCR amplification. Diagnostic errors can occur due to rare sequence variations.

Counseling and informed consent are required for Huntington Disease genetic testing. Consent forms are available online at www.aruplab.com.


Phenotype
Number of CAG Repeats
Normal allele Less than or equal to 26
Mutable normal allele 27-35
HD allele with reduced penetrance 36-39
HD allele Greater than or equal to 40

Compliance Statement C: For human genetic inheritable conditions and mutations. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.

Note
Hotline History
N/A
CPT Codes

81271

Components
Component Test Code* Component Chart Name LOINC
0050604 Huntington Disease (HD) Allele 1 49637-2
0050606 Huntington Disease (HD) Allele 2 49638-0
0050607 Huntington Disease (HD) Interpretation 50621-2
2001353 Huntington Disease (HD) - Specimen 31208-2
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • HD genetic testing
  • HTT genetic testing
Huntington Disease (HD) Mutation by PCR