SCA6 (CACNA1A) Genetic Testing (Repeat Expansion)

CPT: 81184
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Special Instructions

This assay is not currently available in New York state.


Expected Turnaround Time

2 - 4 weeks



Specimen Requirements


Specimen

Whole blood


Volume

4 mL


Minimum Volume

1 mL


Container

Lavender-top (EDTA) tube


Collection

Draw blood into EDTA tube.


Storage Instructions

Ship ASAP, but stable up to 5 days post-collection at room temperature. Do not freeze.


Stability Requirements

Temperature

Period

Room temperature

5 days

Refrigerated

5 days

Frozen

Do not freeze


Causes for Rejection

Frozen blood EDTA tube


Test Details


Use

Spinocerebellar ataxias (SCAs), and episodic ataxias are the most common types of ADCAs. SCAs are numbered based upon their time of identification. SCA3 is the most common type of SCA worldwide, followed by SCA2, SCA1, and SCA6. Some of the complicated forms have not been given a SCA number, like Dentatorubral Pallidoluysian Atrophy (DRPLA). Anticipation can be observed in the autosomal dominant ataxias in which CAG trinucleotide repeats occur. Anticipation results from expansion in the number of CAG repeats with transmission of the gene to subsequent generations. Most ADCAs have an overlap in clinical presentation, which makes it hard to differentiate. The most frequent clinical symptoms in all ADCAs are progressive adult-onset gait ataxia (often with hand dysmetria), and dysarthria associated with cerebellar atrophy. The episodic ataxias are characterized by periods of unsteady gait and often associated with nystagmus or dysarthria. Myokymia, vertigo, or hearing loss may occur in some of the subtypes. Permanent ataxia and even cerebellar atrophy may result late in the disease course.


Limitations

This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.


Methodology

Repeat-Primed PCR (QP-PCR)


LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
620127 SCA6 Repeat Expansion 21755-4 230163 Specimen Status N/A
620127 SCA6 Repeat Expansion 21755-4 620128 SCA6 Result 21755-4
620127 SCA6 Repeat Expansion 21755-4 620129 SCA6 Interpretation N/A
620127 SCA6 Repeat Expansion 21755-4 620130 SCA6 Footnotes N/A

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CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2018, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf