A 38-year-old woman undergoing cardiac surgery at R.L. Jalappa Medical College, Kolar, was found to have a rare new Chromer antigen. This breakthrough highlights a critical clinical challenge, as such rare blood groups are generally uncovered only when standard cross-matching across multiple donors fails to yield compatible blood.
Because multiple donor units were found to be completely incompatible with the patient's blood, a detailed work-up was required to source a safe match. Ultimately, the International Blood Group Reference Laboratory (IBGRL) in Bristol investigated the case and identified a brand-new antigen. This discovery officially adds a new blood type to the Cromer system, aptly named CRIB—where 'CR' represents Cromer and 'IB' stands for India-Bengaluru, honouring the location of its discovery.
What is the CRIB blood group, and why is it so rare?
The Chromer blood group system: The system comprises multiple antigens (proteins), some found on almost all individuals (high-prevalence) and others that are rare. In response to a transfusion or pregnancy (in case of females), the body may form a new antibody.
What makes blood types like CRIB, Rhnull ('Golden Blood'), and panreactive blood unique?
Before we understand what Chromer blood group or other rare blood groups are, we need to understand that, as per the International Society of Blood Transfusion, there are more than 47 blood group systems.
When we say we belong to the A, B, AB or O group, we are only referring to the ABO blood group system, which is only one of these 47 systems.
ABO systems: You belong to A group if your red cells have "A" antigen (protein) on your red cells, and you belong to B group if your red cells have B antigen (protein) on your red cells. If you have both A and B proteins on your red cells, you belong to AB, and if you have none (zero), you belong to group "O".
Rh system (positive or negative): Next, when we say you are positive or negative, we are referring to another of these 47 blood group systems, which we call the Rh system. A positive means that, in addition to the A antigen (protein) of the ABO system, you also have another antigen (protein) called the D antigen of the Rh system, which makes you positive for the D antigen. If you do not have D antigen on your red cells, you would be called A negative.
It is the presence or absence of this "D" antigen in the Rh system that makes you Rh(D) positive or Rh(D) negative. However, just as the ABO system has four groups — A, B, AB and O groups — the Rh system can be divided into C, c, D, E, and e types based on the presence or absence of these proteins on the red cells. An individual may or may not have all of these (C, c, D, E, e).
What is golden blood?
Rarely, an individual may lack all the Rh antigens (C, c, D, E, e). Such individuals are called Rh(null). Such a Rh null blood group is very rare, and hence, such a blood type is called the golden type. There are very few of them in the world, and having a rare donor registry of blood donors is useful, as these people cannot receive blood from any Rh(D) positive or Rh(D) negative individual.
While Rh(D) negative individuals lack only the "D" antigen, Rh(null) individuals lack all Rh antigens — C, c, D, E, e. Such blood is more prone to destruction in the body and may lead to anaemia. However, we cannot transfuse Rh-positive blood (any of these 5 antigens), because if we put any foreign protein into the body, it will be destroyed. We therefore need to find another Rh(null) donor, which is impossible in the absence of a national registry.
Why rare blood groups pose a serious clinical challenge
By now, you probably know that blood grouping is much more complex than simply A positive or A negative. There are 47 blood group systems and hundreds of rarer blood groups. It is not practical to group all of them and issue blood.
That's why blood centres do an antibody screening for unexpected antibodies and match donor and patient blood before issue. When a patient develops an antibody against a rare group, then finding blood of the particular type becomes extremely difficult and nearly impossible in many cases. This was one such case, where, fortunately, surgery could be performed without using blood.
The urgent need for rare donor registries in India
We do come across such rare blood groups from time to time, and in the absence of a rare donor registry, we hit a dead end.
The National Institute of Immunohematology in Mumbai is the only institute that can work up such difficult cases in India.
The role of technology in detecting and tracking rare blood groups
The use of advanced reference laboratories, such as the International Blood Group Reference Laboratory in Bristol, for antigen identification and classification, which helped label the new CRIB blood group.
Raising awareness: Why every donor counts
The case exemplifies how every unique blood donor contributes to medical discovery, and how rare antibodies can only be tackled by increasing awareness and voluntary participation in registries.
The author is a consultant & head of transfusion medicine at Manipal Hospital, Bangalore.
The opinions expressed in this article are those of the author and do not purport to reflect the opinions or views of THE WEEK.
