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Chromosome Analysis, Blood

Test code(s) 14596

This is an outdated version of this FAQ. It was effective 03/25/2014  to 04/18/2016.

The current version is available here.

Question 1. My patient has a family history of a chromosome abnormality. Chromosomes were reported as normal. Do these results guarantee that my patient has not inherited the 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 cytogenetic studies that can be done on my patient?

Yes, there are other studies that may be appropriate. There are many causes for developmental 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 (test code 16478, Chromosomal Microarray, Postnatal, ClariSure® Oligo-SNP). 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 this assay rule out?

This assay can rule out:

  1. Trisomies such as trisomy 21 (Down syndrome), trisomy 18, trisomy 13
  2. Sex chromosome abnormalities such as Turner (45,X) and Klinefelter (XXY) syndromes.
  3. Most rearrangements, including Robertsonian translocations, reciprocal translocations, and inversions
  4. Marker chromosomes
  5. Mosaicism at or above 14% (at a 95% confidence level)      
  6. Most microscopically visible structural abnormalities

Question 4. What disorders cannot be detected by this assay?

This assay cannot detect:

  1. Most microdeletion syndromes, including DiGeorge, Prader Willi, Angelman, Williams, and Smith Magenis
  2. Mosaicism below 14% (at a 95% confidence level)
  3. Fragile X syndrome
  4. Single gene disorders such as cystic fibrosis, Marfan syndrome, neurofibromatosis, etc.
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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