BACKGROUND AND OBJECTIVES: RHD*03N.01 (RHD*DIIIa-CEVS(4-7)-D) and RHD*01N.06(RHD*D-CEVS(4-7)-D) are hybrid alleles that encode a partial C antigen, resulting in increased risk of C alloimmunization in individuals without a conventional C antigen. As detection of the hybrid alleles remains challenging, new markers can aid accurate identification, ensuring provision of C-negative blood to individuals at risk. MATERIALS AND METHODS: To identify breakpoint regions and distinct intronic single nucleotide variations (SNVs) of the hybrid alleles, Pacific Bioscience (PacBio) long-read sequencing was performed in two patients with RHD*DIIIa-CEVS(4-7)-D and one patient with RHD*D-CEVS(4-7)-D; two patients without hybrid alleles served as controls. Association of the identified SNVs with RHD*DIIIa-CEVS(4-7)-D was subsequently evaluated in 910 patients with sickle cell disease. RESULTS: The 5' breakpoint region of RHD*DIIIa-CEVS(4-7)-D was found in intron 3 at chr1:25293827-25293837 (RHD c.486+3036-3046) and chr1:25293907-25293980 (RHD c. 486+3116-3189) for the two patients. The 5' breakpoint region of RHD*D-CEVS(4-7)-D was at chr1:25294633-25295072 (RHD c.486+3842-4281). Both hybrid alleles had identical 3' breakpoint region in intron 7 at chr1:25310252-25310377 (RHD c.1073+3523-3648). Three intronic SNVs were found in RHD*DIIIa-CEVS(4-7)-D: chr1:25293603 (RHD c.486+2812) G>A, chr1:25293891 (RHD c.486+3100) A>G in intron 3; chr1:25310934 (RHD c.1073+4205) T>C in intron 7. In 910 patients, the SNVs demonstrated high sensitivities (94.83%, 94.83%, 96.55%) and specificities (99.88%, 99.88%, 99.88%) in detecting RHD*DIIIa-CEVS(4-7)-D. One SNV, chr1:25294894 (RHD c.486+4103) T>C in intron 3, was identified in RHD*D-CEVS(4-7)-D, but not confirmed due to lack of additional carriers. CONCLUSION: Three intronic SNVs can be used to accurately identify RHD*DIIIa-CEVS(4-7)-D.
Chang et al. (Mon,) studied this question.