Prevalence of ABO and RhD blood group phenotypes in the Croatian population and in patients with severe COVID-19 in Croatia.

BACKGROUND: The aim of this study was to determine the distribution of ABO and RhD blood group phenotypes in the general population in the Republic of Croatia and among hospitalized patients with severe COVID-19. MATERIALS AND METHODS: Data on ABO and RhD blood groups of all blood donors in Croatia (who donated blood during the period 2015-2020) and patients and pregnant women tested at the Croatian Institute of Transfusion Medicine during the 2-year period, 2019-2020, were obtained from the e-Delphyn blood bank information system. A total of 614,673 results were analyzed in this group. The other group consisted of 780 COVID-19 patients hospitalized with severe COVID-19. Data are presented as total number and percentages and a comparison of proportions test was performed. RESULTS: The most frequent ABO phenotype in the general population is A (38%), followed by O (37%), B (18%) and AB (7%). RhD positive individuals accounted for 81% of the general population and RhD negative for the other 19%. Among COVID-19 patients, phenotype A was the most frequent (42%), followed by phenotypes O (32%), B (17%) and AB (9%). Thus blood group A was significantly more common among COVID-19 patients than among the general population, whereas blood group O was significantly less frequent. DISCUSSION: This study provides the first official results of the distribution of ABO and RhD blood group phenotypes in the general population in Croatia. Moreover, this study confirms other researchers' observations about the predominance of the A blood group phenotype among COVID-19 patients.

D variants in the population of D-negative blood donors in the north-eastern region of Croatia.

OBJECTIVES: The aim of this study was to determine RHESUS D GENE (RHD) allelic variants among Croatian D-negative blood donors and compare our results with respective data from other European countries. BACKGROUND: Altered or reduced D antigen expression can result in D variants, which can be mistyped and can lead to the alloimmunisation of the blood recipient. RHD genotyping can distinguish D variants: weak D, partial D and DEL, thus preventing alloimmunisation. MATERIAL/METHODS: A total of 6523 samples obtained from D-negative Croatian donors were screened for the presence of RHD using the real-time polymerase chain reaction (PCR) method. PCR-SSP was performed for D variant genotyping by using commercial genotyping kits (Inno-Train, Kronberg, Germany). Genomic DNA sequencing for all 10 exons of the RHD was performed when the genotyping kits failed to assign a D variant. RESULTS: RHD molecular screening revealed 23 (0.35%) RHD-PCR positive samples, all C/E positive, in decreasing frequency: 11 hybrid RHD-CE (2-9) D-CE variants, 4 weak partial D type 11 and 2 weak D type 2. Six samples remained unresolved and were sequenced. For 12 of 23 samples (excluding large hybrids), an adsorption/elution of anti-D serum was performed, confirming that all 12 were RhD+. The calculated frequency of clinically significant D alleles in RhD-negative blood donors was 1:543 (0.18%) or 1:53 (1.89%) in C/E blood donors. CONCLUSION: Data on the significant frequency of D variants among serologically D-negative blood donors in the north-eastern region of Croatia could help in introducing RHD molecular screening of blood donors in a routine workflow.