Of the main D variants, a patient with partial D (or partial weak D) may develop anti-D to the D epitopes that they lack. Moreover, partial D red cells adsorb little anti-D, thus leaving enough free RhIG to suppress immunization.
However, most laboratories do not routinely differentiate between D variants and instead rely on routine tests and associated test protocols to determine a mother's Rh status for RhIG administration. Policies differ between countries and even within countries.
- Some labs do not test pregnant patients for weak D and rely on routine D typing to determine Rh status.
- Some labs perform weak D tests on pregnant patients who appear to be Rh negative and, if weak D, do NOT inject with RhIG.
- Some labs perform weak D tests on pregnant patients who appear to be Rh negative and, if weak D, inject with RhIG based on the possibility that they may be partial D and capable of forming anti-D.
The laboratory's RhIG procedure should clarify when or if patients of childbearing age with weak or discrepant Rh(D) typings should receive RhIG.
