A Novel ABO Gene Variant Leads to Discrepant Results in Forward/Reverse and Molecular Blood Grouping.
BACKGROUND
Discrepant results in antigen and reverse ABO blood typing are often caused by a variant ABO gene. Molecular analysis can help to characterize such variants. Here, we describe the identification of a novel ABO gene variant in a patient with aberrant ABO phenotype and discrepant genotyping results.


METHODS
A patient with discrepant results in automated forward and reverse ABO phenotyping was further investigated by serological (gel and tube technique) and molecular (commercial and inhouse PCR-SSP, DNA sequencing) methods. A PCR-SSP system was established to screen the novel mutation in 1,820 blood donors.


RESULTS
Standard serological tests confirmed blood group O, however, only anti-B isoagglutinins were present. A monoclonal anti-AB antibody detected very weak agglutination in gel technique. Standard ABO genotyping using PCR-SSP led to discrepant results (O(1)/O(1) or O(1)/A) depending on the test system used. ABO exon re-sequencing identified a novel missense mutation in exon 6 at position 248A>G (Asp83Gly) in the binding region of PCR-SSP primers for the detection of 261G alleles. Blood donors with regular ABO blood groups were all negative for the 248G allele designated Aw34.


CONCLUSIONS
The novel ABO gene variant Aw34 is associated with very weak A antigen expression and absent anti-A isoagglutinins. The mutation is located in exon 6 close to the O(1)-specific 261G deletion in the binding region of PCR-SSP primers. Presumably, depending on the primer concentration used in commercial ABO genotyping kits, the mutation could lead to a false-negative reaction.
Institute of Transfusion Medicine and Immunology, Medical Faculty Mannheim, Heidelberg University; German Red Cross Blood Service Baden-Württemberg - Hessen, Mannheim, Magdeburg, Germany.
Meike
M
Goebel
Institute of Transfusion Medicine and Immunohematology, Otto-von-Guericke University Hospital, Magdeburg, Germany.
Ines
I
Halm-Heinrich
Institute of Transfusion Medicine and Immunohematology, Otto-von-Guericke University Hospital, Magdeburg, Germany.
Andreas
A
Parkner
Institute of Transfusion Medicine and Immunology, Medical Faculty Mannheim, Heidelberg University; German Red Cross Blood Service Baden-Württemberg - Hessen, Mannheim, Magdeburg, Germany.
Gabriele
G
Rink
Institute of Transfusion Medicine and Immunohematology, Otto-von-Guericke University Hospital, Magdeburg, Germany.
Marcell U
MU
Heim
Institute of Transfusion Medicine and Immunology, Medical Faculty Mannheim, Heidelberg University; German Red Cross Blood Service Baden-Württemberg - Hessen, Mannheim, Magdeburg, Germany.
Peter
P
Bugert
ABO phenotyping and genotyping; ABO sequencing ABO gene variant; PCR-SSP