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RHD Gene Detection, Fetal
Test Code16592
CPT Codes
81403<br><strong>This test is not available for New York patient testing.</strong>
Preferred Specimen
10 mL whole blood collected in an EDTA (lavender-top) tube
Minimum Volume
5 mL
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 6 days
Refrigerated: Unacceptable
Frozen: Unacceptable
Refrigerated: Unacceptable
Frozen: Unacceptable
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Clotted • Streck tubes • Pregnancy before 10 weeks
Methodology
Real-Time Polymerase Chain Reaction
FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Setup Schedule
Set up: Daily; Report available: 6-8 days
Reference Range
See Laboratory Report
Clinical Significance
This test offers molecular detection by real-time PCR of the RHD gene in fetal cell-free DNA (cfDNA) isolated from maternal plasma. In RhD-negative pregnant persons, this test can help determine the fetal RhD status to assess risk for RhD alloimmunization-associated hemolytic disease of the fetus and newborn (HDFN). As this is a screening test, it is not intended to be used for diagnostic purposes.
If cfDNA testing results suggest an RhD-negative fetus, Rh immune globulin (RhIG) may not need to be routinely administered, but such determination should be based on clinical judgement and current peer reviewed guidelines [1].
Although rare, false positive or false negative results may occur. A fetus with a positive RhD result may present with an RhD-negative phenotype due to a variant in the RHD gene undetected by this screening assay. Detection of a weak fetal RHD genotype may generate a false positive RhD result in a fetus that may present with an RhD negative phenotype at birth.
This test cannot distinguish between a positive RHD genotype and a negative RhD phenotype in the presence of RHD pseudogene interference. All results should be interpreted in the context of pertinent clinical findings, relevant obstetric history and laboratory data based on a clear understanding of the value and limitations of the test data.
References
1. ACOG Clinical Practice Update: Paternal and Fetal Genotyping in the Management of Alloimmunization in Pregnancy. Obstetrics & Gynecology. 2024; 144(2): p e47-e49.
If cfDNA testing results suggest an RhD-negative fetus, Rh immune globulin (RhIG) may not need to be routinely administered, but such determination should be based on clinical judgement and current peer reviewed guidelines [1].
Although rare, false positive or false negative results may occur. A fetus with a positive RhD result may present with an RhD-negative phenotype due to a variant in the RHD gene undetected by this screening assay. Detection of a weak fetal RHD genotype may generate a false positive RhD result in a fetus that may present with an RhD negative phenotype at birth.
This test cannot distinguish between a positive RHD genotype and a negative RhD phenotype in the presence of RHD pseudogene interference. All results should be interpreted in the context of pertinent clinical findings, relevant obstetric history and laboratory data based on a clear understanding of the value and limitations of the test data.
References
1. ACOG Clinical Practice Update: Paternal and Fetal Genotyping in the Management of Alloimmunization in Pregnancy. Obstetrics & Gynecology. 2024; 144(2): p e47-e49.
