I prepared this policy for HMC Qatar, which did not perform genotyping.
Weakened expression of the D antigen may be due to either quantitative or qualitative defects. Qualitative defects (partial or mosaic D) are uncommon.
Patients with quantitative defects have the whole D molecule and will not make anti-D upon exposure to D-positive RBCs.
Patients with partial or mosaic D may form antibodies against the portion of the D molecule they lack. However, not all partial D types may make anti-D upon exposure. Since we cannot specifically test for this condition, we shall consider females of child-bearing age with weak D as potentially partial D and use D-negative RBCs.
Genotyping for the D gene may define better which partial D types need to receive RhIG or D-negative transfusions.
Weak D is defined as weak (1+ or weaker) reactions with one or more routine reagents or reactions only at antiglobulin phase (i.e. Du testing).
- All donor units must be tested by a method to detect weak D phenotype. If such testing is positive, the donor unit must be labelled as D-positive and be used routinely for D-positive patients.
- Weak-D females of child-bearing ages (<50) should receive D-negative RBCs.
- Weak-D males may receive D-positive RBCs unless they are a potential recipient of chronic transfusions (e.g. thalassemia, sickle cell disease, etc.)
Technical Manual, Current Edition, American Association of Blood Banks, Bethesda, Maryland, USA
Standards for Blood Banks and Transfusion Services, Current Edition, AABB, Bethesda, MD, USA