Case History

Which one of the following is the highest incidence antigen in the Rh blood group system?

  1.        Antigen D
  2.        Antigen C
  3.        Antigen E
  4.       Antigen e

Answer is D.

A. D Rationale: Approximately 85% of random RBC's are D antigen positive.

B. C Rationale: Approximately 70% of random RBC's are C antigen positive.

C. c Rationale: Approximately 80% of random RBC's are c antigen positive.

D. E Rationale: Approximately 30% of random RBC's are E antigen positive.

E. e Rationale: Approximately 98% of random RBC's are e antigen positive.

Major points of discussion

The most common Rh- negative Fisher-Race haplotype is ce. The most common Rh- positive Fisher-Race haplotype in whites is DCe and in blacks is Dce. Notice that all of the common haplotypes described above include e, which is the highest frequency antigen found in the Rh System. One gene codes for D antigen and a second gene codes for CE antigens. The frequency of the Rh antigens varies by race/ethnicity (for example, RhD-positive is more common in Asian populations).


Case contributed by: Sohaila Soltani, M.D., Transfusion Medicine Fellow, UAB Pathology