Distribution of Rhesus blood group antigens and weak D alleles in the population of Albania

Abstract

Background: Determination of Rhesus (Rh) status is of critical importance in the field of both transfusion and obstetric medicine. As the distribution of Rh phenotypes was unknown in the Albanian population, we investigated the donor population in Albania to estimate the prevalence of each phenotype, as well as to identify and characterise the variants at the molecular level.

Materials and methods: A total of 38,836 blood donors were phenotyped for Rh D, C, c, E and e antigens by routine serological methods, and samples with reduced D antigen expression underwent molecular characterisation by a Tm-shift genotyping method and direct sequencing.

Results: Among all donors 89.00% and 10.86% were D-positive and D-negative, respectively, while 0.14% (n=55) of the donors were found to be weak D-positive. Overall 45/55 samples (81.8%) were resolved by Tm-shift screening, showing that approximately 67% of the variant D alleles were weak D type 1, while weak D type 3 (9.1%) and weak D type 2 (3.6%) were less common. A novel c.932A>G (p.Y311C) variant was also found in the heterozygous state by direct sequencing.

Discussion: This extensive study reveals the distribution of Rh phenotypes in the Albanian population, the low prevalence of individuals with a weak D phenotype, and the specific pattern of distribution of the three most common variant alleles in this Caucasian population.

Figure 1

Direct sequencing of RHD and RHCE exon 6 in a heterozygous RHD c.932A>G sample (electropherograms). Positions of interest are indicated by an arrow (i.e., c.916 and c.932) and a black line (c.939+21_24). RHD (NM_016124.4) and RHCE (NM_020485.4) reference sequences with bold, underlined gene-specific nucleotides are mentioned below the electropherograms. Dots in the RHCE sequence indicate homology with the RHD sequence.