- Irish Blood Transfusion Service

Weak D Genotyping

Our Weak D Genotype Test is designed to identify individuals who are Weak D Type 1, 2 or 3 and those who are any other Weak D Type. The result of testing will be reported as:

  • Weak D Type 1, 2 or 3 detected
  • Weak D Type 1, 2 or 3 NOT detected

If a patient’s red cells reaction weaker than expected with routine anti-D reagents (typically ≤2+ reaction strength), they may be one of currently 147 recognised Weak D Types.

The risk of alloimmunisation is dependent on which Weak D Type is identified. Weak D Types 1, 2 or 3 do not develop alloanti-D and should be treated as RhD-positive, both for transfusion and obstetric purposes.

Individuals with other Weak D Types can develop alloanti-D, or it is not possible to determine the probability or type of immunisation. These individuals should be treated as RhD-negative, both for transfusion and obstetric purposes.d how to send samples.

Not all patients with a Weak D phenotype will need genotyping. Please see our User Guide for a suggested testing algorithm which can act as a guide for referral. However, all samples will be genotyped.

Please send copies of your RhD phenotyping results.

See Customer Resources for details on sample labelling requirements, Request Forms and how to send samples.