Variants of RhD – current testing and clinical consequences

Anti‐D (‐ RH 1) of the Rh blood group system is clinically important as it causes haemolytic transfusion reactions and haemolytic disease of the fetus and newborn. Although most people are either D+ or D−, there is a plethora of D variants, often categorized as either weak D or partial D. These two types are inadequately defined and the dichotomy is potentially misleading. DVI is the D variant most commonly associated with anti‐D production and UK guidelines recommend that patients are tested with anti‐D reagents that do not react with DVI . Weak D types 1, 2, and 3 are seldom, if ever, associated with alloanti‐D production, so a policy recommendation would be to treat patients with those D variants as D+, to preserve D− stocks, whereas patients with all other D variants would be treated as D−. All donors with D variant red cells, including DVI , should be treated as D+.