The science of blood transfusion is complex and multifaceted. Determining the correct blood product to transfuse into a patient is of utmost importance to his or her care and recovery.

This decision comes down to more than just matching the ABO group of the donor and recipient. The surface of our red blood cells contains antigens (like a protein) that determine a person’s specific blood type.

Doctors and scientists have discovered more than 600 of these antigens. Their presence or absence creates our individual blood types.

Currently, there are 33 recognized blood group systems. Each group has its own unique combination of antigens.

What is rare?

Your blood type is considered rare if it is missing a common antigen or combination of antigens that most people have.
 
Someone with a rare blood type lacks antigens that 99% of people are positive for. Those with an extremely rare blood type lack antigens that 99.9% of people are positive for.

For example, a person’s blood type is considered rare if only 1 other person in 1,000 shares their same special combination of antigens. To be considered extremely rare, those numbers jump to 1 in 10,000.

Compatibility is key

For patients with rare or extremely rare blood types, receiving transfusions from compatible donors is key to successful treatment and recovery.

If a person receives a transfusion of blood that contains antigens his or her own blood does not contain, the patient’s immune system could attack the foreign antigen and have deadly results.

Rarity runs in the family

Blood type is an inherited trait, and many of the factors that determine the unique makeup of your blood type are related to your ethnicity. Certain blood types are more common in certain ethnicities. 

That means it can be nearly impossible to find a specific rare blood type for a person of one ethnicity in a donor of another ethnicity. It is vitally important to have a steady supply of blood donations from people of all ethnicities to help meet the needs of our diverse patient population.

If you have a rare blood type, it may run in your family. If you have biological siblings, they could have rare blood too. 

Talk to your family members about the importance of blood donation and encourage them to give with you. The donation process is more fun when you save lives together!

The power of rare blood types

You may have heard about the search for blood donors that took place after 3-year-old Zainab was diagnosed with a rare pediatric cancer. The South Florida girl has extraordinarily rare blood and needed very specific blood donors to help save her life as she battled neuroblastoma.

Because she is missing the common antigen known as Indian B, she can only receive blood from people who are also missing that antigen. The only people likely to have the blood she needs are of Indian, Iranian or Pakistani descent. Of those populations, less than 4% are likely to be missing the Indian B antigen.

OneBlood tested more than 4,000 units in the search for blood donors who would be compatible with Zainab, ultimately finding five donors who could contribute to her fight. Because the special blood she needed was available, Zainab was able to undergo the necessary treatment, surgery and transplant to continue her battle.

Learn more about Zainab’s story and the power of rare blood types here.