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Interpretive Handbook

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Test 89338 :
Chromosome Analysis, Spontaneous Breakage Analysis, Blood

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.

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

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.

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.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Gatti R: Ataxia-Telangiectasia. Available from URL: on February 16, 2012

2. Concanon P, Gatti R: Nijmegen Breakage Syndrome. Available from URL: 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: Chapter 9: Chromosome instability syndromes. In Human Cytogenetics: Malignancy and Acquired Abnormalities. Edited by DE Rooney. Oxford University Press, 2001, pp 227-254

6. Ray JH, German J: The chromosome breakage syndromes: clinical features, cytogenetics, and molecular genetics. In Clinical Laboratory Medicine. Edited by KD McClatchey. Lippincott Williams and Wilkins, 2002