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Chromosome Analysis, Neonatal Blood

Test code(s) 16843

Question 1. My patient has a family history of a chromosome abnormality, but his/her chromosome analysis was reported as normal. Does this result guarantee that he/she doesn’t have the familial chromosome abnormality?

No, please call Quest Genomic Client Services at 866-GENE-INFO to discuss this case with a genetic counselor. Documentation of the specific genetic test result in the family is necessary to determine if the type of testing that was performed on your patient is sufficient to identify the familial chromosome abnormality.

Question 2. My patient has a developmental disorder, but his/her chromosome analysis was 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 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 Quest Diagnostics Genomic Client Services at 866-GENE-INFO to discuss the case with a genetic counselor and for information on adding another test.

Question 3. What chromosomal disorders does this assay rule out?

This assay rules out:

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

If mosaicism is suspected please contact Quest Genomic Client Services at 866-GENE-INFO for help selecting   the appropriate test.

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

This assay cannot detect:

  • Most microdeletion syndromes, including DiGeorge, Prader Willi, Angelman, Williams, and Smith Magenis
  • Mosaicism below 14% (at a 95% confidence level)
  • Very subtle rearrangements
  • Gains/losses smaller than the resolution of chromosome analysis
  • Fragile X syndrome
  • Single gene disorders such as cystic fibrosis, Marfan syndrome, neurofibromatosis, etc.

If a microdeletion syndrome or mosaicism is suspected, please contact Quest Genomic Client Services at 866-GENE-INFO for help selecting the appropriate test.

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.75 Version: 1
Version 1 effective 07/09/2015 to present
Version 0 effective 9/12/2012 to 07/08/2015