Unit Code 81176:
Spinobulbar Muscular Atrophy (Kennedy's Disease), Molecular Analysis
Useful For 
Suggests clinical disorders or settings where the test may be helpful
Molecular confirmation of clinically suspected cases of sporadic or
familial SBMA
Presymptomatic testing for individuals with a family history of SBMA
and a documented expansion in the androgen receptor (AR) gene
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
| • | Molecular Genetics-Congenital Inherited Diseases Patient Information Sheet |
| • | Informed Consent for DNA Testing |
Method Name A short description of the method used to perform the test
A polymerase chain reaction (PCR)-based assay is utilized
to detect expansion-type mutations (CAG repeats) within
the androgen receptor gene.
(PCR is utilized pursuant to a license agreement with Roche
Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Spinobulbar Musc Atrophy, Kennedy's
Ordering Mnemonic An alternate Mayo code (to the Unit Code) for a test
SBMA
Aliases Lists additional common names for a test, as an aid in searching
Kennedy's Disease
SBMA (Spinal and bulbar muscular atrophy)
Soft-SBMA
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
"Molecular Genetics-Congenital Inherited Diseases
Patient Information Sheet" (Supply T521 or see Special
Instructions) is required for all orders. If not ordering
electronically, please submit the above information sheet along
with a "Molecular Genetics Request Form" (Supply T245) with the
specimen.
Specimen must arrive within 96 hours of draw.
Draw blood in a lavender-top (EDTA) tube or a yellow-top
(ACD) tube, and send 2 mL of EDTA or ACD whole blood in
original VACUTAINER. Invert several times to mix blood.
Forward unprocessed whole blood promptly at ambient
temperature.
New York Clients: Informed consent is required.
Please document on the request form or electronic
order that a copy is on file. An "Informed Consent
for DNA Testing" (Supply T576) is available. See
Special Instructions for a copy of the form.
Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
0.2 mL
The amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Transport Temperature Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) and unacceptable transport temperature(s) are also included. The preferred transport temperature is listed first, followed by the alternate acceptable temperature (if appropriate) and lastly, the unacceptable transport temperature(s).
Ambient\Refrig OK\Frozen NO
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
Icteric:
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
X-linked spinal and bulbar muscular atrophy (SBMA, or Kennedy's
disease) is characterized by onset of progressive muscle weakness,
atrophy, and fasciculations typically in the 4th or 5th decade of life.
Affected patients also have signs of androgen insensitivity such as
gynecomastia, reduced fertility, and testicular atrophy. The clinical
severity and age at onset can be quite variable, even within families.
Because this is an X-linked disease, males manifest this disorder and
females are generally asymptomatic carriers. However, there have
been reports of female carriers who exhibit symptoms such as muscle
weakness and cramping.
SBMA is caused by an expansion of the CAG trinucleotide repeat in
exon 1 of the human androgen receptor (AR) gene. This trinucleotide
repeat is polymorphic in the general population, with the number of
repeats ranging from 11 to 34. The number of repeats found in affected
individuals can range from 38 to 62. There is no consensus as to the
clinical significance of alleles of 35 CAG repeats and literature
suggests that alleles of 36 to 37 CAG repeats may be associated with
reduced penetrance. As with other trinucleotide repeat disorders,
anticipation is frequently observed, and larger CAG expansions are
associated with earlier onset and a more rapid clinical progression.
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 alleles: 11-34 CAG repeats
Abnormal alleles: 36-62 CAG 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
CAG-repeat amplification in the AR gene in an affected family member to
confirm that molecular expansion is the underlying mechanism of
disease in the family.
We strongly recommend that patients undergoing predictive testing
receive genetic counseling both prior to testing and after results are
available.
Predictive testing of an asymptomatic child is not recommended.
Test results should be interpreted in the context of clinical findings,
family history, and other laboratory data. Errors in our interpretation of
results may occur if information given is inaccurate or incomplete.
A previous bone marrow transplant from an allogenic donor will interfere
with testing. Call Mayo Medical Laboratories for instructions for testing
patients who have received a bone marrow transplant.
Current evidence suggests that the majority of individuals with SBMA
have a CAG-repeat expansion. However, we cannot eliminate the
possibility that another type of mutation not detected by our assay is
present within the AR gene.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Pinsky L, Beitel LK, Trifiro MA: Spinobulbar Muscular Atrophy. In The
Metabolic and Molecular Basis of Inherited Disease. Vol. 4. 8th edition.
Edited by CR Scriver. AL Beaudet, WS Sly, et al. New York, McGraw-
Hill Book Company, 2001, pp 4147-4157
Method Description Describes how the test is performed and provides a method-specific reference
Direct mutation analysis. A PCR-based assay is used to detect
amplification-type mutations (CAG-repeat expansion) within the AR
gene. (Doyu M, Sobue G, Mukai E, et al: Severity of X-linked recessive
bulbospinal neuronopathy correlated with size of the tandem CAG
repeat in androgen receptor gene. Ann Neurol 1992;31:707-710)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Tuesday; 2 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
5 days
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
11 days
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
3 months
Performing Laboratory Location The location of the laboratory that performs the test
List Fee Provides the Mayo Medical Laboratories list fee for performing the test
$471.10
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test was developed and its performance characteristics
determined by Laboratory Medicine and Pathology, Mayo Clinic.
This test has not been cleared or approved by the U.S. Food
and Drug Administration.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each unit code or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
83890/Molecular isolation or extraction
83898/Amplification, target, each nucleic acid sequence
83909/Separation and identification by high-resolution technique
83912/Interpretation and report
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