Weak and Variant RhD Antigens – Characteristics andFrequency of Types Investigated in 1997–2002 in the Reference Laboratory for Immunohaematology

Overview

RhD antigen is the main antigen of the Rh system and belongs to the clinically most relevant antigensof the human red cell. Correct determination of the RhD status is important for the prevention ofhaemolytic transfusion reactions and for prevention and treatment of the haemolytic disease of thenewborn. Numerous atypical forms of RhD protein (D variants = qualitative changes; weak D =quantitative changes) complicate RhD assessment. Knowledge of the frequency of variant and weak Dtypes in the population is helpful for the choice of optimal anti-D reagents and for transfusion andimmunoprophylactic recommendations. The authors present the first extensive study of atypical Dantigens in the Czech population.Most frequent variants detected were D VI (10x), DFR (7x) and D VII(6x), relatively frequent (3x) was DCS variant, which was so far detected only in the local population.In our study we detected also DIVb and rare variants DOL and DYO. Alloimmunization was detectedin patients with variants D IIIc, D VII and DNB. In carriers atypical D antigen in Rh phenotype R1r thefrequency of D variants was cca 7% while in Rh phenotype R2r was five times more frequent – Rhphenotype could serve as a guide for safer substitution and prophylaxis before definitive assessmentof the D weak or variant type. Possibilities and limits of use of commercial kits for D pheno- andgenotyping in the Czech population are discussed.

Key words:
RhD antigen, variant D antigens, weak D antigens, frequency, detection by monoclonalantibodies and PCR-SSP