Weak D phenotypes and transfusion safety: where do we stand in daily practice?

Area of Science:

• Transfusion Medicine
• Immunology
• Genetics

Background:

• Weak D variants (Types 1, 2, 3) prevent immunization upon D antigen exposure.
• Molecular methods efficiently type weak D variants but are not widely used.
• Analysis of weak D serologic typing in Caucasian patients and proposed transfusion strategy.

Purpose of the Study:

• To analyze serologic typing practices for weak D variants.
• To propose a transfusion strategy for weak D recipients.
• To evaluate the utility of sensitive serologic methods for weak D detection.

Main Methods:

• Routine laboratory samples (ddCcee or ddccEe) were tested using the indirect antiglobulin test (D(u) test).
• D(u)-positive samples were screened for weak D alleles (Types 1, 2, 3).
• Testing utilized immunoglobulin M (IgM) anti-D reagents in a fully automated device.

Main Results:

• Out of 55,162 samples, 468 were identified as ddCcee or ddccEe.
• Ninety-three samples were D(u)-positive, leading to D+ transfusion assignment.
• 73% of D(u)-positive samples were weak D alleles Type 1, 2, or 3; most reacted with automated IgM anti-D reagents.

Conclusions:

• Sensitive serologic methods effectively detect weak D Types 1, 2, and 3.
• A definitive cutoff for distinguishing clinically significant variants is lacking.
• Assign D+ status for weak D recipients, excluding women of childbearing age, due to potential rare partial D or other weak D variants.