Weak D phenotypes and transfusion safety: where do we stand in daily practice?
BACKGROUND
Weak D Types 1, 2, and 3 recipients cannot be immunized when exposed to D antigen. Molecular biology is very efficient to type weak D variants but rarely implemented in daily practice. The serologic typing practice of weak D in a Caucasian patient population was analyzed and a transfusion strategy is proposed.


METHODS
Samples typed either ddCcee or ddccEe in routine laboratories were tested with the indirect antiglobulin test (D(u) test). D(u)-positive samples were screened for weak D alleles Types 1, 2, and 3 and further tested with immunoglobulin M (IgM) anti-D reagents, used in a fully automated device.


RESULTS
A total of 468 of 55,162 samples were found to be ddCcee or ddccEe. Ninety-three expressed weak D after the D(u) test leading to D+ assignment for transfusion. Seventy-three percent of D(u)-positive samples were weak D alleles Type 1, 2, or 3. Almost all weak D Types 1, 2, and 3 were positive with IgM reagents in gel matrix with an automated device. Other variants that could be potentially associated with anti-D alloimmunization, however, were also positive.


CONCLUSIONS
Serology is very sensitive to detect weak D Types 1, 2, and 3, but there is no cutoff to distinguish variants of clinical significance. When molecular analysis is not available, it is proposed that a D+ status for blood recipients found to be weak D with a sensitive method be assigned, except for women of childbearing age or younger, because of the remaining possibility to be partial D or other rare weak D who can be immunized.
Noizat-Pirenne
France
F
French Blood Establishment, Island of France, Créteil, France. france.noizat-pirenne@efs.sante.fr
Verdier
Martine
M
Lejealle
Annette
A
Mercadier
Anne
A
Bonin
Philippe
P
Peltier-Pujol
Françoise
F
Fialaire-Legendre
Anne
A
Tournamille
Christophe
C
Bierling
Philippe
P
Ansart-Pirenne
Hélène
H
D000483:Alleles; D001331:Automation; D001788:Blood Grouping and Crossmatching / Q000379:methods* / Q000592:standards*; D001803:Blood Transfusion / Q000379:methods* / Q000592:standards*; D018604:Epitope Mapping; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D007202:Indicators and Reagents; D010641:Phenotype; D012204:Rh-Hr Blood-Group System / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D012680:Sensitivity and Specificity; D012698:Serologic Tests
D007075:Immunoglobulin M; D007202:Indicators and Reagents; D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen