Chromosome Analysis, Spontaneous Breakage Analysis, Blood
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.
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.
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: 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