Rare blood types are more common than most people realize. There are four major blood types — A, B, AB, and O — but over 600 different antigens can be found within the blood types themselves. Problems arise when a transfusion is needed and antigens are not compatible. Approximately one person in 1,000 has a rare blood type. Approximately one person in 10,000 is classified as having a very rare blood type.
A special concern for people with rare blood types is the risk of a transfusion reaction. Common blood types share common antigen characteristics. For instance, people with AB-positive blood can donate and receive from anyone. People with O-negative blood can transfuse to anyone, but can only receive a transfusion from another O-negative individual. The possible combinations are lengthy and complex, and become even more so for people with rare blood types.
Reactions occur when a rare-blood patient in need of a transfusion receives the wrong or incompatible type. The results of such a transfusion can result in shock, kidney failure, and even death. Blood banks typically have very low or nonexistent supplies. An individual with rare blood is often encouraged to regularly donate his own blood, having it stored at a local hospital in case of emergency.
A person with rare blood might be reluctant to travel outside his home country, due to the possibility that a suitable donor might not be available. This is especially true if one travels to East Asia, where blood supplies are limited. In the US, the American Red Cross and the American Association of Blood Banks (AABB) have established the American Rare Donor Program (ARDP). The ARDP maintains a database of donors, and stockpiles rare blood supplies. The European Data Base and Bank of Frozen Blood of Rare Groups, operating under the auspices of the European Directorate for the Qualities of Medicines and Healthcare, operates a similar program.
Some rare blood types are found within specific ethnic groups. Duffy-negative blood is found only within a small percentage of the African American population, and is extremely difficult to locate when needed. Transfusions can usually be received only from another African American donor, preferably one with the same rare type. Even more rare is the Bombay blood group, which is incompatible with all A, B, and O types. Those whose blood is of this group are compatible only with each other.
It is estimated that, worldwide, someone requires a blood transfusion every three seconds. This translates to over 23,000 people per day. A person with rare blood should not be fearful of such statistics, but he should take preventative measures to assure that his specific type is available when needed.