In RhD-negative pregnant patients whose reproductive partners are RhD-positive or have unknown RhD-status, the RHD Gene Detection, Fetal test can help determine the fetal RhD status to assess risk for RhD alloimmunization-associated hemolytic disease of the fetus and newborn (HDFN).
Test Code: 16592
The RHD Gene Detection, Fetal test is performed on cell-free DNA (cfDNA) isolated from maternal blood. This cfDNA contains both maternal DNA and fetal derived DNA from placental cells. The isolated DNA is analyzed using real-time (RT-PCR) targeting exon 4 of the RHD gene.
RHD Gene Detection, Fetal screens for the presence or absence of the RHD gene in cfDNA isolated from maternal plasma. In an RhD-negative pregnant person, the presence of the RHD gene in cfDNA is consistent with an RhD-positive fetus. The absence of the gene is consistent with an RhD-negative fetus.
The RHD Gene Detection, Fetal test is not indicated for pregnant patients with an RhD-positive blood type, or for RhD-negative pregnant patients whose reproductive partner is also RhD-negative.
Yes, the RHD Gene Detection, Fetal test can be performed for twin pregnancies.
Results are typically reported 5 to 7 days after specimens are received in the laboratory. Results are sent to the ordering healthcare provider’s office or to the electronic medical record (EMR).
In rare situations, specimens may not contain enough cell-free DNA. If this happens, test results cannot be obtained, interpreted, or reported. The test can be repeated using newly collected maternal blood specimens.
RHD Gene Detection, Fetal is a screening test. Fetal RHD status can be confirmed using amniocentesis or chorionic villus sampling during pregnancy or using blood testing after birth.
References:
- Isakson P, Pardi C. Evaluation of an automated platform for non-invasive single-exon fetal RHD genotyping early in pregnancy. Blood Transfus. 2023;21(6):472-478. doi:10.2450/2023.0267-22
- Uzunel M, Tiblad E, Mörtberg A, Wikman A. Single-exon approach to non-invasive fetal RHD screening in early pregnancy: An update after 10 years' experience. Vox Sang. 2022;117(11):1296-1301. doi:10.1111/vox.13348
- Wikman AT, Tiblad E, Karlsson A, Olsson ML, Westgren M, Reilly M. Noninvasive single-exon fetal RHD determination in a routine screening program in early pregnancy. Obstet Gynecol. 2012;120(2 Pt 1):227-34. doi:10.1097/AOG.0b013e31825d33d9
- ACOG Clinical Practice Update: Paternal and Fetal Genotyping in the Management of Alloimmunization in Pregnancy. Obstetrics & Gynecology. 2024;144(2):e47-e49. ACOG Practice Advisory: Rho(D) Immune Globulin Shortages. 2024. doi:10.1097/AOG.0000000000005630
- ACOG Practice Advisory. Rho(D) Immune Globulin Shortages. Published March 2024. Updated July 9, 2024. https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2024/03/rhod-immune-globulin-shortages
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 the physician’s education, clinical expertise, and assessment of the patient.
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