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Chromosome Analysis, High Resolution

Test code(s) 14595X

This is an outdated version of this FAQ. It was effective 08/31/2012 to 09/15/2016.

The current version is available here.

Question 1. My patient has a family history of a chromosome abnormality. My patient's chromosomes were reported as normal. Do these results guarantee that my patient does not have the familial chromosome abnormality?

No, please call 866-GENE-INFO to discuss this case with a genetic counselor. Documentation of the specific genetic abnormality in the family will be necessary to determine the accuracy of the testing that was performed on your patient.

Question 2. My patient has a developmental disorder. Chromosomes were reported as normal. Are there other genetic studies that can be done?

Yes, there are other studies that may be appropriate.  There are many causes for development disorders, some of which are genetic.  In the absence of clinical suspicion for a specific genetic disorder, a microarray analysis may be performed to detect subtle deletions and duplications.  If clinical suspicion exists for a specific disorder, there may be other genetic testing available.  Please contact 866-GENE-INFO to discuss the case with a genetic counselor and for information on adding additional testing. 

Question 3. What chromosome disorders does high resolution chromosome analysis rule out?

High resolution chromosome analysis (test code 14595X) rules out the following:

  • Trisomies such as trisomy 21 (Down syndrome), trisomy 18, and trisomy 13
  • Sex chromosome abnormalities such as Turner syndrome (45,X) and Klinefelter syndrome 47,XXY)
  • Most rearrangements, including Robertsonian translocations, reciprocal translocations, and inversions
  • Most marker chromosomes
  • Mosaicism above 14% (at a 95% confidence level) 

Question 4. What disorders cannot be detected by high resolution chromosome analysis?

High resolution chromosome analysis (test code 14595X) cannot detect the following:

  • Most microdeletion syndromes, including DiGeorge, Prader-Willi, Angelman, Williams, and Smith Magenis syndromes
  • Mosaicism below 14% (at a 95% confidence level)
  • Fragile X syndrome
  • Single gene disorders such as cystic fibrosis, Marfan syndrome, neurofibromatosis, etc.
  • Very small or subtle gains, losses, or rearrangements

Question 5. How is this test different from routine chromosome analysis?

High resolution studies allow more detailed analysis of chromosome structure, which may detect more subtle chromosome abnormalities not detectable by routine studies. High resolution chromosome analysis is suggested for patients who have a family history of a particular abnormality and for patients who have very specific clinical features.

This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.

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