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Chromosome Analysis, Tissue

Test code(s) 14593(X)

Question 1. What are the best specimens to submit from products of conception (POC)?

The entire POC or a portion of the POC containing placental membrane, villi, umbilical cord, and fetal parts is optimal. In cases of early gestation pregnancy loss, membranes and villi may be the only fetal tissue available. In later pregnancy loss, other fetal tissues including umbilical cord, skin, cartilage (rib), pericardium, internal membrane, and diaphragm should also be submitted if available. Placenta specimens should be collected from the fetal side of the placenta. Amniotic fluid, cord blood, and/or cardiac blood may also be submitted, using a different test code. To choose the appropriate test code, or to discuss a particular case with a genetic counselor, please call 866-GENE-INFO.

Question 2.What is the collection procedure for POC specimens?

POC specimens should be collected in as sterile a manner as possible and immediately placed in transport medium in a sterile urine cup or other sterile containerto reduce cell death and contamination. Quest Diagnostics provides "POC Transport Media" upon request (a balanced salt solution supplemented with antibiotics and an antimycotic). However, any sterile, balanced salt solution is acceptable (Ringer's solution, Hanks Balanced Salt Solution, etc.). Water is not an acceptable transport medium. If multiple tissue types are available from a POC, please put each tissue type in its own container. Each container should be clearly labeled with the specific tissue type and patient name. All tissue types can be submitted under the same requisition and test code unless multiple gestations. If multiple gestations, please submit POC from each gestation under separate requisitions.

Question 3. How should the POC specimens be stored and transported?

Store and transport POC specimens in a tightly closed container to prevent the specimen from drying out. Store and transport at refrigerated (2-8°C) temperature. Room temperature storage is not recommended, and specimens should never be frozen. Transport as soon as possible, preferably less than 48 hours after collection.

Question 4. Which POC specimens cannot be used for chromosome study?

Any compromised specimens that would fail to produce analyzable metaphase cells, eg, formalin-fixed specimens, frozen samples, necrotic tissue, or obviously contaminated specimens, cannot be used for chromosome study. Chromosome studies can only be performed on dividing cells cultured from fresh tissue specimens.

Question 5. What information should be sent along with the POC specimens?

Please send patient clinical and pregnancy history, any significant family history, and gestational age information.

Question 6. Multiple fetal anomalies were detected by ultrasound or autopsy, but chromosome analysis was normal. Are there further studies that can be done to test for a genetic disorder in the fetus?

Yes, there are other studies that may be appropriate. There are many causes of fetal anomalies, some of which are genetic. In the absence of clinical suspicion for a specific genetic disorder, a microarray analysis may be performed on the products of conception (POC) to detect subtle deletions and duplications (test code 90929, Chromosomal Microarray, POC, 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 another test.

Question 7. My patient has a personal or family history of a chromosome abnormality. Chromosome analysis on products of conception tissue was reported as normal. Do these results guarantee that the fetus did not have the chromosome abnormality in the family?

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 the fetus.

Question 8. The tissue chromosome analysis was reported as a growth failure. Are there any other studies that can be attempted on the tissue to determine if the fetus has a chromosome abnormality?

When tissue fails to grow, a standard chromosome analysis is impossible to perform. There are two tests that may be considered to provide some information regarding the fetal chromosomes on tissue samples that fail to grow. FISH, Products of Conception Panel (test code 14820X) will provide information regarding the number of copies of chromosomes 13,16,18,21,22,X and Y. A Chromosomal Microarray, POC, ClariSure® Oligo-SNP (test code 90929) may be performed to detect subtle deletions and duplications of chromosome material. Please contact 866-GENE-INFO to discuss the case with a genetic counselor and for information on adding additional testing.

Question 9. Which chromosome abnormalities does the Chromosome Analysis, Tissue test rule out?

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

Question 10. Which disorders cannot be detected by the Chromosome Analysis, Tissue test?

  • Most microdeletion syndromes, including DiGeorge, Prader-Willi, Angelman, Williams, and Smith-Magenis
  • Subtle rearrangements and small gains/losses
  • Mosaicism below 14%
  • Fragile X syndrome
  • Single gene disorders such as cystic fibrosis, Marfan syndrome, neurofibromatosis, etc

Question 11. The report indicates that maternal cell contamination (MCC) is a potential pitfall; is there a test that can be done to test for MCC?

Yes. Maternal Cell Contamination Study, STR Analysis (test code 10262) may be ordered on a maternal blood sample. Ideally, the maternal sample should be submitted with the tissue sample. If you are considering adding MCC studies to a completed case, please call 866-GENE-INFO to speak with a genetic counselor.

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 FAQ 77 Version: 1
 
Version 1 effective 09/22/2014 to present