A novel ABO allele with a 21-bp duplication identified in two unrelated European individuals with weak A expression.

OBJECTIVES: To carry out genetic and serological analyses of a Swiss blood donor and a Danish patient carrying an aberrant ABO phenotype with weak A expression. BACKGROUND: ABO is the most clinically important blood group system but also one of the most complex. The system antigens are determined by carbohydrate structures generated by A and B glycosyltransferases encoded by the ABO gene. Genetic variants of ABO may encode a glycosyltransferase with reduced activity, leading to weak expression of A antigen. METHODS: Samples from two individuals were examined using genetic testing and extended immunohaematological evaluation, including standard serological methods, flow cytometry and analysis of plasma glycosyltransferase activity. RESULTS: Both individuals were serologically determined to be Aweak B. Genetic testing revealed that both were heterozygous for a novel ABO*A1.01-like allele with an in-frame duplication of 21 nucleotides in exon 7 (c.543_563dup), leading to the insertion of seven amino acids (QDVSMRR). Flow cytometric testing of native red blood cells (RBCs) showed very weak A antigen expression. This was in accordance with the enzyme activity test. CONCLUSION: In summary, we describe a novel A allele with a duplication of 21 nucleotides in exon 7 that significantly decreases the enzyme activity and leads to very weak expression of A antigen. (200 words).

The Remarkable Journey of a Low-Frequency Alloantibody.

Herein we describe a case of febrile non-hemolytic reaction (FNHTR) in a 64-year-old male 20 min after the transfusion of one red blood cell unit. 20 days prior the patient had undergone an allogeneic hematopoietic stem cell transplantation (HCT) from an unrelated donor with minor ABO disparity. The patient had been treated for plasma cell myeloma with multiple transfusions in the past, but no transfusion reactions or alloimmunization had been reported.

Implementation of a mandatory donor RHD screening in Switzerland.

Starting in 2013, blood donors must be tested at least using: (1) one monoclonal anti-D and one anti-CDE (alternatively full RhCcEe phenotyping), and (2) all RhD negative donors must be tested for RHD exons 5 and 10 plus one further exonic, or intronic RHD specificity, according to the guidelines of the Blood Transfusion Service of the Swiss Red Cross (BTS SRC). In 2012 an adequate stock of RHD screened donors was built. Of all 25,370 RhD negative Swiss donors tested in 2012, 20,015 tested at BTS Berne and 5355 at BTS Zürich, showed 120 (0.47%) RHD positivity. Thirty-seven (0.15%) had to be redefined as RhD positive. Routine molecular RHD screening is reliable, rapid and cost-effective and provides safer RBC units in Switzerland.