Weak D and partial D in Slovenian population through serology and genotyping

Weak D red cell phenotype (formerly D^u) exhibits weaker serological reaction with anti-D antibodies. Weak D occurs in 0.2% to 1% of whites and is caused by qualitatively altered RhD proteins called partial D or normal, only weakly expressed RhD proteins that are called weak D. Partial D genes are hybrid alleles between RHD an RHCE genes. 23 partial RHD alleles are described. Weak D phenotypes with reduced expression are likely to posses the normal RHD gene, but the latest findings indicate that weak D alleles carry at least one point mutation. The aim of the present work was to answer an important question how to approach partial and weak D identification in diagnostic use and if it is possible to distinguish between partial D and weak D using commercially available anti-D reagents for routine use. We also wanted to evaluate D-screen kit for partial D identification. We compared phenotypes identified by serological testing and genotypes identified by RHD Multiplex PCR and D^VII specific ASPA PCR. Our results showed that it is not possible to distinguish between partial and weak D using commercially available anti-D reagents for routine use. D-screen proved to be useful for D^VI and D^VII identification, whereas for partial D^DFR identification we must look for another set of monoclonal antibodies or simply use genotyping methods. In 44 samples with not interpretable serological results out of 80 we found all RHD specific exons present and we classified the samples as weak D. Fourteen types of weak D with at least one point mutation were recently proposed. Designing of allele specific PCRs for identification of proposed types of weak D is in progress.