Determine the number of copies of the RHD gene. Does not identify or distinguish between partial and weak RHD genotypes.
Polymerase Chain Reaction/Fluorescence Monitoring
Fetal Genotyping: Amniotic fluid OR two T-25 flasks at 80 percent confluency of cultured amniocytes. If the client is unable to culture amniocytes, this can be arranged by contacting ARUP Client Services at (800) 522-2787.
WITH Maternal Cell Contamination Specimen (see Remarks): Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Parental Genotyping: Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Amniotic Fluid: Transport 10 mL unspun fluid. (Min: 5 mL)
Cultured Amniocytes: Fill flasks with culture media. Transport two T-25 flasks at 80 percent confluency of cultured amniocytes filled with culture media. Backup cultures must be retained the client's institution until testing is complete.
Maternal Cell Contamination Specimen: Transport 3 mL whole blood (Min: 1 mL)
Whole Blood (Parental Genotyping): Transport 3 mL whole blood. (Min: 1 mL)
Amniotic fluid: Room temperature.
Cultured Amniocytes: CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to liability of cells.
Whole Blood or Maternal Cell Contamination Specimen: Refrigerated.
Maternal specimen is recommended for proper test interpretation if contamination of the fetal specimen from the mother is suspected. Order Maternal Cell Contamination. Patient History Form is available on the ARUP website or by contacting ARUP Client Services.
Fetal Specimen: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Whole Blood or Maternal Cell Contamination Specimen: Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Background Information for RhD Gene (RHD) Copy Number:
Characteristics: Fetal or neonatal erythroblastosis and hydrops.
Incidence of RHD-negative genotype: 15 percent Caucasians, 5 percent African Americans, less than 1 percent Asians
Inheritance: Autosomal recessive
Cause: Maternal-fetal Rh D antigen incompatibility
Methods: Determine the presence of the RHD exons 5, 7, and a 37 base pair insertion in the intron 3/exon 4 boundary by PCR and fluorescence monitoring.
Allelic height ratios are used to determine the number of copies of RHD as compared to RHCE.
Limitations: Bloody amniotic fluid specimens may give false-negative results because of maternal cell contamination; specificity may be compromised by mutations in primer sites or those outside the RHD exons examined; fetuses predicted to be unaffected should continue to be monitored by noninvasive means. Diagnostic errors can occur due to rare sequence variations.
Analytic Sensitivity and Specificity: Greater than 99 percent
Clinical Sensitivity: Greater than 98 percent
For quality assurance purposes, ARUP Laboratories will confirm the above result at no charge following delivery. Order Confirmation of Fetal Testing and include a copy of the original fetal report (or the mother's name and date of birth) with the test submission. Please contact an ARUP genetic counselor at (800) 242-2787 extension 2141 prior to specimen submission.
Laboratory Developed Test (LDT)
Whole blood is acceptable for paternal specimens.
|Component Test Code*||Component Chart Name||LOINC|
|0050422||RhD Gene (RHD) Copy Number||35465-4|
|0051369||RhD Gene (RHD) Copy Number Specimen||31208-2|
- RHD Gene
- RHD genotyping