Test Catalog

Test Id : CSTB

CSTB Gene, Repeat Expansion Analysis, Varies

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

Molecular confirmation of clinically suspected CSTB-related progressive myoclonic epilepsy

 

Identifying full penetrance dodecamer repeat expansions within CSTB known to cause CSTB-related progressive myoclonic epilepsy, allowing for predictive testing of at-risk family members

 

Impacting patient treatment and management through the identification of a specific underlying etiology for epilepsy (eg, directing appropriate use of anti-epileptic drugs and other treatment modalities)

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 CCC-CGC-CCC-GCG dodecamer repeat expansions in the promoter region of CSTB to confirm a molecular diagnosis of CSTB-related progressive myoclonic epilepsy, also known as progressive myoclonic epilepsy type 1 (EPM1).

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

CSTB, Repeat Expansion Analysis

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

Progressive myoclonic epilepsy type 1

EPM1

Dodecamer repeat expansion

CSTB-related progressive myoclonic epilepsy

Baltic myoclonus

Baltic myoclonic epilepsy

Mediterranean myoclonus

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Specimen Type
Describes the specimen type validated for testing

Varies

Ordering Guidance

This test only detects dodecamer repeat expansions. If testing for both dodecamer repeat expansions and other CSTB variants is requested, order a custom gene panel for the CSTB gene. For more information see CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, 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.

Specimen Type: Whole blood

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 whole blood specimen in original tube. Do not aliquot.

Specimen Stability Information: Ambient (preferred)/Refrigerated

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

Forms

1. New York Clients-Informed consent is required. Please 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.

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

All specimens will be evaluated by 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 CSTB-related progressive myoclonic epilepsy

 

Identifying full penetrance dodecamer repeat expansions within CSTB known to cause CSTB-related progressive myoclonic epilepsy, allowing for predictive testing of at-risk family members

 

Impacting patient treatment and management through the identification of a specific underlying etiology for epilepsy (eg, directing appropriate use of anti-epileptic drugs and other treatment modalities)

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 CCC-CGC-CCC-GCG dodecamer repeat expansions in the promoter region of CSTB to confirm a molecular diagnosis of CSTB-related progressive myoclonic epilepsy, also known as progressive myoclonic epilepsy type 1 (EPM1).

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

CSTB-related progressive myoclonic epilepsy (PME), also known as progressive myoclonic epilepsy type 1 (EPM1) or Unverricht-Lundborg disease, is the most common and least severe of the collective progressive myoclonic epilepsies. CSTB-related PME is inherited in an autosomal recessive pattern and is associated with inter- and intrafamilial variability. Individuals with CSTB-related PME have normal early development with onset of symptoms typically in the first or second decade of life. CSTB-related PME is characterized by involuntary myoclonus that is action- or stimulus-precipitated. Individuals with the condition are at increased risk for seizures, including tonic-clonic, absence, psychomotor and focal motor. The condition is progressive, leading to wheelchair dependence in some individuals. Later symptoms may also include ataxia, incoordination, intention tremor, dysarthria, mood disorders, and mild cognitive decline.

 

CSTB-related PME is caused by disease-causing variants in the CSTB gene. An expansion of a dodecamer repeat sequence in the promoter region of the CSTB gene accounts for approximately 90% of disease-causing variants (99% in Finnish individuals). Full penetrance CSTB expansions are greater than or equal to 30 repeats, while normal alleles are typically 2 or 3 repeats. Allele sizes between 5 and 29 repeats are of unclear significance. The remainder of disease-causing variants are sequence variants including missense, nonsense, splice site variants, and small deletions and duplications. Genotype/phenotype correlation suggests that individuals who are homozygous for nonexpansion variants or compound heterozygous for one expansion allele and one nonexpansion allele have earlier onset and more severe symptoms than those individuals with biallelic expansion alleles. Instability of the repeat expansion has been reported with vertical transmission, including both minimal expansion and contraction of repeat sizes. Alleles in the uncertain range are not associated with symptoms of CSTB-related PME but may demonstrate instability with transmission. Since repeat alleles in this size range have rarely been reported, the risk of repeat expansion into the full penetrance allele range (>29 repeats) is not fully understood. Additionally, correlation of repeat size with onset of symptoms is unclear.

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.

Normal: <5 dodecamer repeats

Repeat Size of Uncertain Significance: 5-29 dodecamer repeats

Full Penetrance Expansion: >29 dodecamer 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 molecular etiology of disease in an affected family member to confirm that a CSTB repeat expansion is the underlying mechanism of disease in the family. Specifically, this assay will not detect nonrepeat expansion variants and progressive myoclonic epilepsy may be caused by variants in other genes.

 

It is 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 test interpretation may occur if the provided information is inaccurate or incomplete.

 

Rare variants (ie, polymorphisms) exist which could lead to false-negative results.

 

Bone marrow transplants from allogenic donors will interfere with testing. Call Mayo Clinic Laboratories for instructions for testing patients who have received a bone marrow transplant.

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

1. Lehesjoki AE, Koskimiemi M: Progressive myoclonus epilepsy of Unverricht-Lundborg type. Epilepsia. 1999;40 Suppl 3:23-28

2. Hypponen J, Aikia M, Joensuu T, et al: Refining the phenotype of Unverricht-Lundborg disease (EPM1): a population-wide Finnish study. Neurology. 2015 Apr 14;84(15):1529-1536

3. Canafoglia L, Gennaro E, Capovilla G, et al: Electroclinical presentation and genotype-phenotype relationships in patients with Unverricht-Lundborg disease carrying compound heterozygous CSTB point and indel mutations. Epilepsia. 2012 Dec;53(12):2120-2127

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 combined amplicon-length and repeat-primed polymerase chain reaction-based assay is utilized to detect expansions of a dodecamer repeat region in the CSTB 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.

Varies

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.

28 to 42 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.

81188

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
CSTB CSTB, Repeat Expansion Analysis 41110-8
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.
616516 Result Summary 50397-9
616517 Result 82939-0
616518 Interpretation 69047-9
616519 Reason for Referral 42349-1
616520 Specimen 31208-2
616521 Method 85069-3
616522 Source 31208-2
616523 Released By 18771-6

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

Test Update Resources

Change Type Effective Date
New Test 2022-06-02