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Test ID CSTB CSTB Gene, Repeat Expansion Analysis, 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

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


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


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.

Useful For

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)

Method Name

Polymerase Chain Reaction (PCR)

Reporting Name

CSTB, Repeat Expansion Analysis

Specimen Type


Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Ambient (preferred)

Reference Values

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.

Day(s) Performed


Report Available

28 to 42 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

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


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CSTB CSTB, Repeat Expansion Analysis 41110-8


Result ID Test Result Name Result LOINC Value
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

Testing Algorithm

For more information see Epilepsy: Unexplained Refractory and/or Familial Testing Algorithm