Identification of RHD alleles with the potential of anti-D immunization among seemingly D- blood donors in Upper Austria.
BACKGROUND
Aberrant RHD alleles leading to a reduced expression of D antigen on the red blood cell (RBC) surface may be mistyped as D- by serology. To quantify the occurrence of weak D, DEL, and D+/- chimera among apparent D- first-time blood donors, polymerase chain reaction (PCR) screening was implemented as a routine service.


METHODS
A total of 23,330 pretyped D- samples were tested for RHD markers in Exons 4, 7, and 10 in pools of 20 by PCR. Samples with positive results in PCR were reevaluated by exon-specific PCRs, DNA sequencing, and serologic methods.


RESULTS
Among 94 PCR-positive samples, 74 exhibited a weak D or DEL phenotype, dubbed weak D type 1, weak D type 2, weak D type 5, weak D type 32, weak D type 4.3, RHD(M295I), RHD(del147), and RHD(1227G>A). The most prevalent alleles were weak D type 4.3 (n = 31) and RHD(IVS3+1G>A) (n = 24).


CONCLUSIONS
As a clinical consequence, 74 blood donor samples carrying weak D and DEL phenotypes with the potential of causing secondary immunizations in recipients were reclassified as D+. Those samples were reliably amplified by RHD Exon 7 PCR; therefore, its usage in the Upper Austrian population is recommended. The association of the weak D type 4.3 samples with a ce leads to the policy that all apparently D- donors should be tested with genotyping methods; otherwise, potentially immunogenic RHD alleles may be overseen.
Polin
Helene
H
Red Cross Transfusion Service of Upper Austria, Krankenhausstrasse 7, Linz, Austria. helene.polin@blutz.o.redcross.or.at
Danzer
Martin
M
Gaszner
Waltraud
W
Broda
Doris
D
St-Louis
Maryse
M
Pröll
Johannes
J
Hofer
Katja
K
Gabriel
Christian
C
D000483:Alleles; D001317:Austria; D001782:Blood Donors; D001788:Blood Grouping and Crossmatching / Q000379:methods; D015331:Cohort Studies; D004252:DNA Mutational Analysis; D005787:Gene Frequency; D006801:Humans; D011110:Polymorphism, Genetic; D011237:Predictive Value of Tests; D012204:Rh-Hr Blood-Group System / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D018029:Rho(D) Immune Globulin / Q000032:analysis / Q000097:blood*; D012698:Serologic Tests
D012204:Rh-Hr Blood-Group System; D018029:Rho(D) Immune Globulin; C026410:Rho(D) antigen