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Maternal Cell Contamination
|Utilization Guidelines||Contamination of prenatal amniotic fluid or chorionic villi samples with maternal cells or tissue may lead to misinterpretation of prenatal diagnostic tests, particularly in determination of true fetal heterozygosity. Maternal contamination of prenatal samples is assessed by genotyping maternal and fetal DNA at fourteen different autosomal short-tandem repeats loci with heterozygosity rates ranging from 70-93%. In addition, a short-tandem repeat in each the X and Y chromosome is also included in the panel to supplement the autosomal markers and to identify sex chromosomes aneuploidies. This assay has the ability to detect maternal DNA contamination in as low as 3% of fetal DNA.
Tests with long turn-around times (ie. Molecular based tests and Microarrays) should only be requested on an inpatient if the result is going to affect the inpatient management.
If the patient will likely be discharged before the result will be available, the test should be requested after discharge. (NOTE: UCSF Medical Center is not reimbursed for inpatient testing).
An exception to the above may be appropriate if there is a possibility the patient will not survive to be discharged and the information is important for diagnosis and/or family decisions/management (ie. recurrence risk).
|Performed by||Medical Genomics - Molecular Diagnostics|
|In House Availability||Run 1x per week as needed, Monday or Wednesday, day shift only|
|Method||PCR and capillary electrophoresis|
|Collection Instructions||Do not collect sample in heparin. Keep sample refrigerated for overnight or longer storage.
For UCSF Samples (from remote sites) Click here for sample collection instructions
For NON-UCSF Samples Click here for Requisition form & Account set-up instructions. Note we only do institutional billing.
|Container type||Lavender top preferred Blue top (Citrate) and Yellow top (ACD) acceptable|
|Amount to Collect||3 mL blood|
|Sample type||EDTA whole blood from mother of fetus. Should only be ordered in conjunction with prenatal genetic testing on either amniotic fluid or chorionic villi.|
|Preferred volume||3 mL blood|
|Min. Volume||1.5 mL blood|
|UCSF Rejection Criteria||Heparinized whole blood received.|
|Processing notes||Do not centrifuge the specimen. Store at room temperature. Refrigerated samples are acceptable|
|Turn around times||10-14 days|
|Additional information||An interpretation of this test by a laboratory physician will automatically be performed and billed for separately.
These tests were developed and their performance characteristics determined by the Clinical Laboratories at the Medical Center at UC San Francisco. They have not been cleared or approved by the U.S. FDA
|LDT or Mod FDA?||Yes|
|Last Updated||1/22/2014 8:59:58 AM|