Test Catalog

Test Id : SCAP

Order This Test

Spinocerebellar Ataxia Repeat Expansion Panel, Varies

Download
Overview

Test Catalog

Useful For
Suggests clinical disorders or settings where the test may be helpful

Molecular confirmation of clinically suspected spinocerebellar ataxia

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

This test assesses for CAG repeat expansions within the ATXN1, ATXN2, ATXN3, CACNA1A, and ATXN7 genes, associated with spinocerebellar ataxia (SCA) type 1, SCA2, SCA3, SCA6, and SCA7. Additionally, testing for ATXN1 assesses for CAT trinucleotides that interrupt the CAG repeat tract.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Polymerase Chain Reaction (PCR)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Spinocerebellar Ataxia Panel

Aliases
Lists additional common names for a test, as an aid in searching

Spinocerebellar ataxia type 1

Spinocerebellar ataxia type 2

Spinocerebellar ataxia type 3

Spinocerebellar ataxia type 6

Spinocerebellar ataxia type 7

SCA1

SCA2

SCA3

SCA6

SCA7

Specimen Type
Describes the specimen type validated for testing

Varies

Shipping Instructions

Specimen preferred to arrive within 96 hours of collection.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

 

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube. Do not aliquot.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826).

2. Molecular Genetics: Neurology Patient Information

3. If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

  Specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Varies Ambient (preferred)
Frozen
Refrigerated

Useful For
Suggests clinical disorders or settings where the test may be helpful

Molecular confirmation of clinically suspected spinocerebellar ataxia

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

This test assesses for CAG repeat expansions within the ATXN1, ATXN2, ATXN3, CACNA1A, and ATXN7 genes, associated with spinocerebellar ataxia (SCA) type 1, SCA2, SCA3, SCA6, and SCA7. Additionally, testing for ATXN1 assesses for CAT trinucleotides that interrupt the CAG repeat tract.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Spinocerebellar Ataxia Type 1:

Spinocerebellar ataxia type 1 (SCA1) is characterized by progressive ataxia, dysarthria, eventual deterioration of bulbar functions, and ophthalmoplegia. Onset typically occurs in the 3rd to 4th decade of life. Most individuals present with difficulties in gait or slurred speech. SCA1 is caused by an expansion of the cytosine-adenine-guanine (CAG) trinucleotide repeat in the ATXN1 gene. This trinucleotide repeat is polymorphic in the general population, with the number of benign repeats ranging from 6 to 37. The pathogenicity of the repeat is dependent on the presence or absence of cytosine-adenine-thymine (CAT) trinucleotide repeats that interrupt the CAG repeats. Therefore, individuals with 36 to 37 uninterrupted CAG repeats are predisposed to having a child with an expanded allele. In affected individuals, the CAG expansions are greater than 38 uninterrupted CAG repeats or greater than 44 repeats regardless of the presence or absence of CAT repeat interruptions. The presence of CAT repeats in an individual with 36 to 43 repeats is considered normal and not pathogenic. In contrast, 38 repeats without CAT repeats is of uncertain significance. There is a report of an individual with very last onset SCA1 with 38 repeats. Reduced penetrance has been associated with 44 repeats. As with other trinucleotide repeat disorders, large CAG expansions are associated with earlier onset and a more severe clinical course.

 

SCA2:

Spinocerebellar ataxia type 2 (SCA2) is characterized by slowly progressive ataxia and dysarthria, and slow saccadic eye movements. The mean age of onset is in the 4th decade, but symptoms may appear from childhood to later adulthood. SCA2 is caused by an expansion of the CAG trinucleotide repeat in the ATXN2 gene. This trinucleotide repeat is polymorphic in the general population, with the number of benign repeats less than 32. However, 29 to 31 heterozygous repeats have been associated with an increased exponential risk for amyotrophic lateral sclerosis (ALS). Additionally, there has been a report of an individual homozygous for 31 repeats with late onset cerebellar ataxia. In contrast, 27 repeats have been associated with a protective effect for ALS. In affected individuals the CAG expansion is greater than 34 repeats, with the most common disease-causing alleles have 37 to 39 repeats. Larger CAG expansions are associated with an earlier age of onset but repeat length cannot predict age of onset or disease severity. A CAG expansion of 32 repeats is of unclear clinical significance. Repeats in the 33 to 34 range are associated with reduced penetrance.

 

SCA3:

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is characterized by progressive cerebellar ataxia and pyramidal signs. The age of onset is highly variable but most commonly occurs in the 2nd to 5th decade of life. Individuals may present with gait problems, speech difficulties, clumsiness, or visual blurring. SCA3 is caused by an expansion of the CAG trinucleotide repeat in the ATXN3 gene. This trinucleotide repeat is polymorphic in the general population, with the number of benign repeats ranging from 12 to 44. In affected individuals the CAG expansion ranges from 60 to 87 repeats. A loose correlation exists between repeat length and clinical phenotype. Individuals with 45 to 59 CAG repeats are predisposed to having a child with an expanded allele and may or may not have symptoms themselves. There have been reports of reduced penetrant and nonpenetrant alleles with repeats in this range.

 

SCA6:

Spinocerebellar ataxia type 6 (SCA6) is characterized by adult-onset, slowly progressive cerebellar ataxia, dysarthria, and nystagmus. The mean age of onset is 43 to 52 years. Initial symptoms include unsteadiness, stumbling, and imbalance. SCA6 is caused by an expansion of the CAG trinucleotide repeat in the CACNA1A gene. This trinucleotide repeat is polymorphic in the general population, with the number of benign repeats less than 19. In affected individuals the CAG expansion ranges from 20 to 33 repeats. Larger CAG expansions are associated with an earlier age of onset. A CAG expansion of 19 repeats is of unclear clinical significance. Individuals with 19 CAG repeats are predisposed to having a child with an expanded allele. Additionally, homozygous abnormal expansions have been reported in individuals with younger age of onset and a more severe phenotype.

 

SCA7:

Spinocerebellar ataxia type 7 (SCA7) is characterized by progressive cerebellar ataxia, including dysarthria and dysphagia, and con-rod and retinal dystrophy. Onset ranges from infancy to the 5th or 6th decade of life. SCA7 is caused by an expansion of the CAG trinucleotide repeat in the ATXN7 gene. This trinucleotide repeat is polymorphic in the general population, with the number of benign repeats less than 19. In affected individuals the CAG expansion is greater than 36 repeats. A CAG expansion of 19 to 27 repeats is of unclear clinical significance. Individuals with 28 to 33 repeats are predisposed to having a child with an expanded allele but are unlikely to have symptoms themselves. Thirty-four to 36 repeats is associated with reduced-penetrance, and when symptoms do occur, they are more likely to be associated with later onset and a milder phenotype.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

SPINOCEREBELLAR ATAXIA TYPE 1

Normal alleles: <36 CAG repeats

Normal alleles with CAT interruptions: 36-43 repeats

Intermediate alleles without CAT interruptions: 36-37 repeats

Uncertain significance: 38 repeats

Expanded alleles without CAT interruptions: >38 CAG repeats

Expanded alleles with CAT interruptions: >43 CAG repeats

 

SPINOCEREBELLAR ATAXIA TYPE 2

Normal alleles: <32 repeats

Uncertain significance: 31 homozygous and 32 repeats

Reduced penetrance: 33-34 repeats

Expanded alleles: >34 repeats

 

SPINOCEREBELLAR ATAXIA TYPE 3

Normal alleles: <45 repeats

Intermediate alleles: 45-59 repeats

Expanded alleles: >59 repeats

 

SPINOCEREBELLAR ATAXIA TYPE 6

Normal alleles: <19 repeats

Intermediate alleles: 19 heterozygous repeats

Uncertain significance: 19 homozygous repeats

Expanded alleles: >19 repeats

 

SPINOCEREBELLAR ATAXIA TYPE 7

Normal alleles: <19 repeats

Uncertain significance: 19-27 repeats

Intermediate alleles: 28-33 repeats

Reduced penetrance: 34-36 repeats

Expanded alleles: >36 repeats

 

An interpretive report will be provided.

Interpretation
Provides information to assist in interpretation of the test results

An interpretive report will be provided.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

For predictive testing, it is important to first document the presence of a cytosine-adenine-guanine (CAG)-repeat expansion in an affected family member to confirm that the repeat expansion is the underlying mechanism of disease in the family.

 

It is strongly recommended that patients undergoing predictive testing receive genetic counseling both prior to testing and after results are available.

 

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in the interpretation of results may occur if information given is inaccurate or incomplete.

 

Due to somatic mosaicism, repeat size identified in the peripheral blood specimen may not reflect the repeat size in untested tissues (eg, central nervous system). In addition, a negative result does not rule out the presence of a variant in the mosaic state that may be present but below the limit of detection of this assay (approximately 10%).

 

Rare sequence variants immediately downstream of the spinocerebellar ataxia (SCA) repeat regions may interfere with genotype results but are not expected to affect repeat-primed peaks.

 

Rare undocumented alterations (ie, polymorphisms) in polymerase-chain reaction primer binding regions may lead to false-negative results.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Soong BW, Morrison PJ: Spinocerebellar ataxias. Handb Clin Neurol. 2018;155:143-174. doi: 10.1016/B978-0-444-64189-2.00010-X

2. Buijsen RAM, Toonen LJA, Gardiner SL, et al: Genetics, mechanisms, and therapeutic progress in polyglutamine spinocerebellar ataxias. Neurotherapeutics. 2019 Apr;16(2):263-286. doi: 10.1007/s13311-018-00696-y

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

A polymerase-chain reaction-based assay is used to amplify across the region of the ATXN1, ATXN2, ATXN3, CACNA1A, or ATXN7 genes containing CAG repeats. Additionally, testing assesses for CAT trinucleotides that interrupt the CAG repeat tract within the ATXN1 gene.(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday, Wednesday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

14 to 21 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

Whole Blood: 2 weeks (if available) Extracted DNA: 3 months

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

81178

81179

81180

81181

81184

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
SCAP Spinocerebellar Ataxia Panel In Process
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
609506 Result Summary 21769-5
609507 Result 36911-6
609508 Interpretation 69047-9
609509 Additional Information 48767-8
609510 Specimen 31208-2
609512 Method 85069-3
609513 Disclaimer 62364-5
609514 Released By 18771-6
609511 Source 31208-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports