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DNA Analysis:
RhD Analysis (Fetal)
The majority of individuals have an intact RhD gene and produce RhD antigen on the surface of red blood cells. These individuals are said to be RhD positive. Approximately 10% of individuals are homozygous for a deletion of the RhD gene and are therefore RhD negative. RhD negative individuals do not produce RhD antigen. Pregnant women lacking an intact RhD gene can become sensitized to the RhD antigen when carrying an RhD positive fetus. Hemolytic disease of the newborn (HDN) can occur when an RhD negative mother produces antibodies against RhD antigens on fetal red blood cells. Administration of immune globulin to RhD negative women during pregnancy reduces the risk for HDN but is not effective in all cases. Determination of fetal RhD status is useful in determining pregnancy management of RhD negative mothers.
- RhD negative woman with a history of Rh sensitization
- RhD negative woman with elevated anti-RhD antibody titers
Our laboratory utilizes an allele specific polymerase chain reaction (PCR) amplification assay with gel electrophoresis to determine the presence of an intact RhD gene. The analysis includes amplification of an internal control and multiple target sites within the RhD gene.
Approximately 10% of individuals are homozygous for a deletion of the RhD gene and are therefore RhD negative. In rare cases, a false positive result can be obtained due to the presence of an RhD variant.
Parental blood samples are required to identify the presence of an RhD variant that may affect the interpretation of the prenatal result.
Amniotic fluid: For fetal RhD analysis only, 10ml of amniotic fluid collected in a sterile container. For fetal RhD analysis and fetal karyotype analysis, 20-25 ml of amniotic fluid. Sample should be stored at room temperature. Cultured amniotic fluid cells are required for confirmation of results in some cases.
Blood: 5 cc collected in a purple top (EDTA) or yellow top (acid citrate dextrose) vacutainer tube. Do not centrifuge or freeze. Specimen may be refrigerated or stored at room temperature.
7 days
83891, 83894, 83900, 83901 (3X), 83912
For studies requiring cell culture add 88235
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