RhD alloimmunization by DEL variant missed in donor testing.

INTRODUCTION: Exposure to normal or variably expressed RhD antigens in an antigen-negative individual can elicit an immune response and lead to the formation of clinically significant anti-D alloantibodies. We present the case of anti-D alloimmunization by DEL variant missed in routine blood donor screening. MATERIAL AND METHODS: Blood donors were typed for D antigen using the direct serologic micromethod. Nonreactive samples were confirmed in the indirect antiglobulin method with an IgM/IgG anti-D monoclonal reagent. Genomic DNA was extracted using a commercial QIAamp DNA Blood Mini kit on the QIAcube device (Qiaqen, Germany). RHD genotyping was performed using the PCR-SSP genotyping kits- Ready Gene D weak, Ready Gene D weak screen, Ready Gene CDE, and Ready Gene D AddOn (Inno-Train, Germany). Unidentified alleles were sent for DNA genome sequencing. RESULTS: After identifying DEL positive blood units in RhD negative blood donor pool, a look-back study was performed to determine if their previous donations caused alloimmunization in recipients. Out of 40 D negative recipients, one developed anti-D alloantibody after 45 days. The patient did not receive other RhD positive blood products. Blood donor typed D negative in direct and indirect agglutination method. RHD screening was positive, but RHD genotyping and DNA sequencing showed no mutation indicating the normal genotype. CONCLUSION: Currently used methods in RHD genotyping are insufficient to identify many variant alleles, especially intronic variations. We suggest additional gene investigation including yet unexplored regions of regulation and intron regions to justify our serological finding.

Anti-HBc prevalence among Croatian blood donors in a 14-year period (2004-2017): Assessment of trends, risks and need for implementing routine testing.

OBJECTIVES: The anti-HBc prevalence over a 14-years period (2004-2017), trends, infectivity, residual risk, and need for testing in blood donors (BD) of the Croatian Institute of Transfusion Medicine were assessed. MATERIAL AND METHODS: Anti-HBc was tested in 19,969 BD serum samples collected in 2004 (N=7561), 2013 (N=7318) and 2017 (N=5090). All serums were initially screened for HBsAg, anti-HCV, HIV Ag/Ab, and anti-TP. 2013 and 2017 samples were also tested by ID-NAT. RESULTS: Over a 14-years period, the anti-HBc prevalence significantly decreased among Croatian BD (5.24% in 2004, 2.56% in 2013, and 1.32% in 2017). Similarly, the prevalence of anti-HBc-only profiles decreased from 0.62% in 2004, 0.25% in 2013, and 0.21% in 2017. The 4-time decreasing trend was observed in all age groups of BD from 2017 but mostly among repeat donors (5.90% to 1.38%). First-time donors showed no significant difference in anti-HBc prevalence probably due to their younger age (<29 years) and HBV vaccine status. However, similar anti-HBs carriage rates (80.56%, 87.57%, and 82.09%) were reported in anti-HBc positive donors over the study period. HBsAg and HBV DNA were not detected. No OBI infection was found in the study despite an OBI frequency of 1:10,900 donations previously reported in Croatia. A HBV decreasing residual risks of 68, 88, and 12 per million donations were estimated for years 2004, 2013, and 2017, respectively. CONCLUSION: Anti-HBc testing is an additional measure of preventing HBV infection by transfusion. Implementation of anti-HBc testing will result in the deferral of 1.3% BD and should be supported by cost-benefit analyses.