Test ID: SBK
Chromosome Analysis, Spontaneous Breakage Analysis, Blood
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Evaluating patients with possible chromosome instability syndromes including ataxia telangiectasia and Nijmegen breakage syndrome
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
This test is useful for detecting increased spontaneous chromosomal rearrangement in patients with ataxia telangiectasia (AT) or Nijmegen breakage syndrome (NBS) (chromosomal instability syndromes). Chromosomal instability syndromes are characterized by defects in DNA repair mechanisms or genetic instability. Patients with these syndromes have an increased risk of developing malignant disorders. When blood from affected individuals is cultured and chromosome analysis is performed, an elevated rate of chromosomal rearrangement is observed.
Method Name A short description of the method used to perform the test
72-Hour Culture with Phytohemagglutinin
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Ataxia Telangiectasia (AT)
Chromosome Breakage Disorder
Chromosome Breakage Syndrome
Chromosome Spontaneous Breakage
NBS (Nijmegen Breakage Syndrome)
Nijmegen Breakage Syndrome (NBS)
Specimen Type Describes the specimen type needed for testing
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.
Provide a reason for referral with each specimen. The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.
Container/Tube: Green top (sodium heparin)
Specimen Volume: 5 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Other anticoagulants are not recommended and are harmful to the viability of the cells.
Additional Information: Advise Express Mail or equivalent if not on courier service.
Forms: If not ordering electronically, submit a Cytogenetics/AFP Congenital Disorders Request Form (Supply T238) with the specimen.
Specimen 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.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | Clotted blood |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| WB Sodium Heparin | Ambient (preferred) | |
| Refrigerated | ||
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Chromosomal instability syndromes are autosomal recessive disorders characterized by defects in DNA repair mechanisms or genetic instability. Patients with these disorders have an increased risk of developing malignant disorders. When blood from affected individuals is cultured and chromosome analysis is performed, elevated rates of chromosomal rearrangements are observed.
These disorders include ataxia telangiectasia (AT) and Nijmegen breakage syndrome (NBS). An increased frequency of chromosome rearrangements, including involvement at 7p13, 7q34, 14q11.2, or 14q32, signals a positive result. NBS usually has a higher frequency of cells with chromosome rearrangements than AT and generally does not include the clinical features of ataxia or increased serum alpha-fetoprotein.
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.
An interpretive report will be provided.
Interpretation Provides information to assist in interpretation of the test results
The pattern of chromosome breakage and the number of breaks are compared to a normal control and an interpretive report is provided.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
A normal result does not rule out a diagnosis of ataxia telangiectasia, Nijmegen breakage syndrome, or other chromosome instability syndromes.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Gatti R: Ataxia-Telangiectasia. Available from URL: http://www.ncbi.nlm.nih.gov/books/NBK26468/accessed on February 16, 2012
2. Concanon P, Gatti R: Nijmegen Breakage Syndrome. Available from URL: http://www.ncbi.nlm.nih.gov/books/nbk1176/accessed on February 16, 2012
3. Dewald GW , Noonan KJ, Spurbeck JL, Johnson DD: T-lymphocytes with 7;14 translocations: frequency of occurrence, breakpoints, and clinical and biological significance. Am J Hum Genet 1986 Apr;38(4):520-532
4. Digweed M, Sperling K: Nijmegen breakage syndrome: clinical manifestation of defective response to DNA double-strand breaks. DNA Repair 2004;3:1207-1217
5. Howell RT, Chromosome instability syndromes. Chp 9, p 227-254 in DE Rooney's Human Cytogenetics: Malignancy and Acquired Abnormalities. Oxford University Press, 2001
6. Ray JH & German J. The chromosome breakage syndromes: clinical features, cytogenetics, and molecular genetics, in McClatchey's Clin Lab Med, 2002
Method Description Describes how the test is performed and provides a method-specific reference
In the laboratory, a portion of the whole blood is transferred to a flask containing media with a T-cell mitogen. The cells are incubated for 72 hours at 37 degrees C. In the harvest process, the cells are exposed to colcemid, hypotonic solution, and fixed with glacial acetic acid and methanol. Metaphase cells are dropped onto microscope slides and stained for G-banding with Leischman stain. A concurrent control sample is processed and analyzed. Fifty metaphases from the patient and control are examined to identify chromosome rearrangements. (Unpublished Mayo method)
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.
Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m.-5 p.m. CST.
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.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
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.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
88230-Culture for chromosome analysis, lymphocytes
88248-Chromosome analysis breakage syndromes
88291-Interpretation and report
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 29996 | Specimen | 31208-2 |
| 29997 | Specimen ID | N/A |
| 29998 | Source | N/A |
| 29999 | Order Date | N/A |
| CG370 | Reason For Referral | 42349-1 |
| 30010 | Method | 49549-9 |
| 50473 | Banding Methods | 62359-5 |
| 30015 | Results | N/A |
| 30019 | Interpretaton | N/A |
| 30020 | Amendment | N/A |
| 30021 | Reviewed By | N/A |
| 30022 | Release Date | N/A |
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