RHD positive among C/E+ and D- blood donors in Denmark.

BACKGROUND Many different partial and weak D types have been reported, and most of these are easily detected by serology. However, 17 Del types have also been described, with a very low expression of the D antigen, only detectable by absorption-elution techniques, and these may elicit the development of an anti-D. A genomic test of C/E+ and D- blood donors was initiated, to be able to categorize them correctly as D+ or -. STUDY DESIGN AND METHODS We analyzed all C/E+ and D- donors within our donor population of 22,000 donors with an initial test for RHD Exon 10. In case of a positive reaction, the genotype was further analyzed by sequence-specific polymerase chain reaction or nucleotide sequencing of the RHD gene. CONCLUSIONS Of 233 donors analyzed, seven were found positive for RHD Exon 10, and four of these were Del, corresponding to 1.7%. We report here a new mutation in the RHD gene. A correct assignment of all blood donors as D+ or D- is not possible using serotyping alone; genotyping offers the only exact categorization of all cases.