RhD Gene (RHD) Copy Number

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.

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.