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XSense®, Fragile X with Reflex and Chromosome Analysis, Blood

Test code(s) 16326, 16327 (NY)

The FAQ information attached by the previously provided link has been retired. The link continues to be available for your historic reference. Current FAQs can be viewed at QuestDiagnostics.com/FAQs.

This is an outdated version of FAQ 60. It was effective 11/05/2012 to 06/03/2014.

The current version is available here.

Question 1. My patient has a developmental disorder. Chromosome analysis and fragile X studies were reported as normal. Are there other cytogenetic studies that can be performed 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 1-866-GENE-INFO to discuss the case with a genetic counselor and for information on adding additional testing.

Question 2. My patient has a family history of mental retardation. Chromosome analysis and fragile X studies were reported as normal. Do these results guarantee my patient won’t have a child with mental retardation?

No. Please call 1-866-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 3. What chromosome disorders does this assay rule out?

This assay rules out:

  1. Trisomies such as Down syndrome (trisomy 21), trisomy 18, and trisomy 13
  2. Sex chromosome abnormalities such as Turner and Klinefelter syndromes
  3. Most rearrangements, including Robertsonian translocations, reciprocal translocations, and inversions
  4. Marker chromosomes
  5. Chromosomal mosaicism

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

This assay cannot detect:

  1. Submicroscopic gains or losses of genetic material, including microdeletion syndromes such as DiGeorge and Williams
  2. Low level chromosomal mosaicism
  3. 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.

Document FAQS.60 Revision: 1