Weak D type 67 in four related Canadian blood donors

Area of Science:

• Transfusion Medicine
• Immunology
• Genetics

Background:

• Accurate RhD blood typing is crucial for preventing recipient alloimmunization.
• Existing serologic methods have limitations in detecting all RhD variants.
• The immunogenicity of many RhD variants remains poorly understood.

Observation:

• Four donors with weak D type 67 were initially typed as D-negative using automated microplate and manual tube indirect antiglobulin tests (IAT).
• Subsequent testing with automated solid-phase methods and RHD gene analysis confirmed these donors as D-positive.
• The weak D type 67 variant was consistently identified across serologic and molecular analyses for all four donors.

Findings:

• Automated microplate and manual tube IAT methods failed to detect weak D type 67 in these donors.
• Automated solid-phase testing and RHD gene analysis successfully identified the weak D type 67 variant.
• Transfusion from one of these donors likely led to RhD alloimmunization in a recipient.

Implications:

• Current routine blood typing methods may not identify all D-positive individuals, particularly those with weak D variants like type 67.
• Advanced serologic techniques (solid-phase) and molecular methods are essential for accurate RhD typing.
• Failure to detect weak D variants can lead to alloimmunization, posing risks for future transfusions and pregnancies.