(P-IG-18) Frequency of Mia antigen and Rh phenotypes in Hong Kong Chinese Blood Donors

While the Rh blood group system commonly account for the clinically significant alloantibodies in hospitalized patients, the Mi^a antigen of Miltenberger subsystem of the MNS blood group system is also of concern in this locality. Reported prevalence of anti-Mi^a ranged from 0.20% to 0.56% in local hospital cohorts. As anti-Mi^a has been reported associated with haemolytic transfusion reactions, screening for anti-Mi^a has become a standard practice in pre-transfusion compatibility test in local setting.  In Western countries, Rh/K matching is often employed for selection of red cells for transfusion-dependent patients. On the contrary, the strategy in adopting Rh/Mi^a matching is practiced in many parts of southeast Asia due to difference in frequencies of blood groups and alloantibody specificities.  A study was therefore undertaken to determine the frequencies of Mi^a-positive and different Rh phenotypes in blood donors of Chinese ethnicity to give insight into planning of supply of suitable red cell units to transfusion-dependent patients such as thalassaemia major.
 

Study

Design/Methods:

From 2011 to 2021, 26,879 active donors out of 49,446 ethnic Chinese blood donors with Mi^a phenotyped were analyzed retrospectively (Table 1). The ABO and RhD blood groups were tested by PK7300 or PK7400 (Beckman Coulter, USA) whereas the Rh antigens (C, c, E and e) as well as the Mi^a antigen were typed by tube method using monoclonal antisera (Diagast, France) and monoclonal anti-Mi^a-antiserum (Immucor, Norcross, USA) respectively.  Typing for blood group was performed at least twice in different donations or occasions.
 

Results/Findings:

7.0% (3,481/49,446) of the ethnic Chinese blood donors were Mi^a +. In those active donors who were Rh(D)-positive and Mi^a-negative, 72.8% (17,614/24,194) had CCDee phenotype, 14.4% (3,489/24,194) ccDEE phenotype, 8.6% (2,069/24,194) CcDEe phenotype, 2.4% (582/24,194) CcDee phenotype, 0.9% (223/24,194) ccDEe phenotype and 0.9% (217/24,194) ccDee phenotype. For those who were Rh(D)-negative and Mi^a-negative, 47.6% (390/820) had ccdee phenotype, 38.7% (318/820) Ccdee phenotype, 10.5% (86/820) CCdee, 1.6% (13/820) ccdEe phenotype and 1.6% (13/820) CcdEe phenotype.
 

Conclusions:

It is found that the prevalence of Mi^a+ was 7.0% among ethnic Chinese blood donors in Hong Kong, which may account for a higher frequency of anti-Mi^a in the local population. Together with the highly polymorphic nature of the Rh blood group system and an increased risk of alloimmunization after repeated transfusions, careful consideration should therefore, be given to selecting phenotype-matched blood, particularly for Rh and Mi^a phenotypes, for chronic transfusion-dependent patients.