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Huntington Disease (HTT) Genetic Testing (Repeat Expansion)

CPT: 81271
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Genes Assessed

HTT

Specimen Requirements


Specimen

Blood | Extracted DNA | Cultured Fibroblasts | Muscle | Buccal Cells

Volume

4 mL, 1 swab, or 200 ng of DNA, 75 mg muscle, 90% cell confluency

Container

Blood: Lavender-Top (EDTA) Tube, Buccal Swab from MNG Kit, Tissue or Extracted DNA: Sterile screw capped vial, Cultured cells: T25 flask

Collection

Blood: Specimens should be shipped overnight in a secure container at room temperature. Extracted DNA: Should be shipped overnight at room temperature. If previously frozen, DNA can be shipped in an insulated container with wet or dry ice. Cultured Fibroblasts: T-25 flasks containing fibroblasts should be shipped in an insulated container at room temperature. Flasks should be completely filled with media and cells should be ~90% confluent. Fibroblast samples must be certified free from Mycoplasma. MNG is able to perform this service for a small charge (TC05). For NGS panels, TAT will be extended by 7-14 days if cells are not confluent upon arrival. Muscle: Samples should be shipped frozen in an insulated container with 5-7 lbs. dry ice, overnight. Buccal cells: Should be shipped overnight in a secure container at room temperature.

Storage Instructions

Blood - ship ASAP, but stable up to 5 days post-collection at room temperature. DO NOT FREEZE; Swab - 60 day post-collection room temperature stability; DNA - ship at room temperature after extraction; Fibroblasts - ship flask in insulated container at room temp or refigerated; Muscle - ship in insulated container with 5-7 lbs of dry ice

Stability Requirements

Room Temperature: Blood - 5 days, Swab - 60 days, DNA - 30 days, Muscle - 0 days, Fibroblasts - 2-3 days; Refrigerated: Blood - 5 days, Swab - 60 days, DNA - 30 days, Muscle - 0 days, Fibroblasts - 2-3 days; Frozen: Blood - DO NOT FREEZE, Swab - 60 days, DNA - Indefinitely, Muscle - Indefinitely, Fibroblasts - Indefinitely; Freeze/Thaw: None

Causes for Rejection

Extracted DNA A260:A280 ratio of outside of 1.8-2.0 range; Frozen blood EDTA tube; Thawed and/or fatty muscle sample; Insufficient buccal cell collection

Test Details


Use

Huntington disease (HD) is a neurodegenerative disease of mid-life onset that produces choreic movements and cognitive decline, often accompanied by psychiatric changes. The disease is caused by an expansion of the CAG repeats in exon 1 of the Huntingtin (HTT) gene. It affects ~3 5 out of 100,000 individuals. However, the prevalence of HD exceeds 15 per 100,000 in some populations, mostly of Western European origin. Juvenile-onset HD occurs in approximately 5% of affected patients, is rapidly progressive, and presents with rigidity, spasticity, and intellectual decline before the age of 20 years. The symptoms result from the selective loss of neurons, most notably in the caudate nucleus and putamen, and there is currently no effective treatment.

Limitations

Maximum reportable sizing: 150 repeats

Methodology

Repeat-Primed PCR (QP-PCR)

Recommended MNG Kits

SINGLE Blood Genetic Testing, Buccal Swab Genetic Testing

Z-Code

ZB9AE

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
620016 Huntington Disease Repeat Exp 230163 Specimen Status N/A
620016 Huntington Disease Repeat Exp 620012 HTT Genetic Test Result 53782-9
620016 Huntington Disease Repeat Exp 620165 HTT Genetic Test Int N/A