In the process of blood transfusion, the first consideration is that the blood types must match each other. However, in addition to  ABO blood type, there are more than two hundred blood group antigens on human red blood cells（RBCs）. It is impossible for each person's red blood cells to express all the two hundred kinds of blood group antigens at the same time, but to selectively express some of them.

       Usually, most people express several sets of similar blood group antigens, and a few people have a different combination of blood group antigens than most people. At the same time, there are some blood group antigens expressed on almost all people's RBCs, but some people lack these blood group antigens. In either case, if a person lacks common antigens or possesses uncommon antigens, then this person's blood should be treated as a rare blood type.

       Therefore, when a person's blood type is possible to find a blood type same to him in a thousand people, we call that person's blood type a rare blood type.. Unless you need a blood transfusion, rare blood types, like other blood types, will not cause any problems for you. There are many different types of rare blood types, but the common feature is that they are all hard to find. When a rare blood type is needed, and it is difficult to find a blood donor with the matched rare blood type for a while, serious medical complications may occur and may lead to death.

Therefore, China National Health Commission requires some provincial blood centers to carry out rare blood type screening projects among blood donors starting in 2009. The blood samples of rare blood group donors are stored and the information is recorded..

  In Chinese rare blood group program, we first focus on the rare blood group antigens or phenotype combinations that can cause serious clinical adverse blood transfusion reactions. These rare antigens or combinations often belong to high frequency blood group antigen group, such as VEL, LAN, or several rare variants in some blood group systems, such as JK (a-b-), Lu (a-b-), Rhnull, OH, etc. At the same time, we also screen for blood group antigens that can cause blood transfusion reactions and neonatal hemolysis in the Chinese population, such as Di( a+b-), Fy(a-b+), etc.

It is hoped that through screening, a library of rare blood types of the Chinese population will be initially established. To solve the clinical urgent need for blood of rare blood types, reduce the occurrence of adverse blood transfusion reactions, and improve the efficacy of blood transfusion.