The Rh D polypeptide is a highly immunogenic protein present on the red cell surface of approximately 85% of Caucasians, >90% of Africans and nearly 100% of Asians. Some of the more than 200 RHD alleles lead to a reduced or variable expression of D antigenic epitopes on the red cell surface.1 Patients with these aberrant alleles may be mistyped by serology because many of the alleles do not react equally with all anti-D typing reagents. Most often, discrepancies with historical results are observed when laboratories change methodologies or reagents. It is important to resolve these discrepancies to determine appropriate anti-D prophylaxis for pregnant women and the Rh status for transfusion recipients at risk of making anti-D. In most cases, molecular analyses can be used to identify RHD alleles that can be deemed Rh positive. Presently, Weak D Types 1, 2, 3, and 4.0 can be deemed Rh positive since clinical data indicate that patients who express these alleles have a very low risk of making anti-D.2,3
The Rh D Discrepancy Analysis is not suitable to characterize suspected partial D alleles (e.g. Rh-positive with anti-D). For these cases, please order ‘PARTIAL D ANALYSIS’.
REASONS FOR REFERRAL:
• Resolution of a prenatal Rh D typing discrepancy.
• Resolution of a pre-transfusion Rh D typing discrepancy.