RhD antigen frequency is most common in Asians (99%) and is slightly less common in Blacks (92%) and Caucasians (85%). (1)
Most D-positive phenotypes have a conventional RhD protein; however variations in protein structure can result in either a weak D or partial D phenotype (1-2% of Caucasians). (2) Of note, patients with D variant phenotypes may produce anti-D if immunised with Rh positive red cells and in this situation, it is recommended they be transfused with Rh negative red cells.
Clinically, weak D individuals of types 1, 2, 3, 4.0, 4.1 and 5 can be treated as Rh positive and be transfused with Rh positive red cells, while patients with weak type 4.2-11 and 15 should be treated as Rh negative and transfused with Rh negative red cells. (3, 4)
Partial D individuals can have different epitope expression and induce specific antibody production. As a result, they should be considered Rh negative and transfused with Rh negative red cells.(3, 4)
RhD negative phenotype is most common in Caucasians (15%), less common in Blacks (8%) and rare in Asians (1%). (1)
Classification of Rh Phenotype and Genotype
Serology results from testing red cells with the five main Rh anti-sera, the Rh phenotype and probable RH genotype are shown in the following table:
Rh Positive
| Serology results and combined data | Phenotype | Probable genotype | Shorthand symbol | Approximate % frequency in Australia | Other possible genotypes |
|---|---|---|---|---|---|
| D+ C+ E- c+ e+ | CcDee | CDe/cde | R1r | 35.3 | CDe/cDe cDe/Cde |
| D+ C+ E- c- e+ | CCDee | CDe/CDe | R1R1 | 17.5 | CDe/Cde |
| D+ C+ E+ c+ e+ | CcDEe | CDe/cDE | R1R2 | 12.9 |
CDe/cdE |
| D+ C- E+ c+ e+ | ccDEe | cDE/cde | R2r | 12.4 | cDE/cDe cDe/cdE |
| D+ C- E+ c+ e- | ccDEE | cDE/cDE | R2R2 | 2.4 | cDE/cdE |
| D+ C- E- c+ e+ | ccDee | cDe/cde | R0r | 1.6 | cDe/cDe |
Rh Negative
| Serology results and combined data | Phenotype | Probable genotype | Shorthand symbol | Approximate % frequency in Australia | Other possible genotypes |
|---|---|---|---|---|---|
| D- C- E- c+ e+ | ccdee | cde/cde | rr | 16.7 | |
| D- C+ E- c+ e+ | Ccdee | Cde/cde | r’r | 0.5 | |
| D- C- E+ c+ e+ | ccdEe | cdE/cde | r”r | 0.7 |
Notes: Frequencies are based on blood group statistics of Australian blood donors; Cells giving a positive reaction with anti-C may be further subdivided by testing with anti-Cw; Other Rh genotypes may be found but all have a frequency of <0.2%.
References
- Dean L.Blood Groups and Red Cell Antigens [Internet]. Bethesda (MD): National Center for Biotechnology Information (US): 2005. Chapter 7, The Rh blood group. Available from: http://www.ncbi.nlm.nih.gov/books/NBK2269/
- Reid ME et al. The Blood Group Antigen Facts Book. 3rd edition. Elsevier, London, 2012
- Rizzo C et al. Weak D and partial D: our experience in daily activity. Blood Transfus. 2012 Apr; 10(2): 235-236
- Daniels G. Variants of RhD – current testing and clinical consequences. British Journal of Haematology 2013; 161: 461-470