CRIB — A Groundbreaking Addition to Blood Group Science

The recent discovery of the CRIB blood group marks a significant advancement in transfusion medicine, presenting unique challenges and opportunities for critical care, prenatal diagnostics, and global blood donation protocols. This information is crucial for professionals involved in patient care, especially those managing complex transfusions and surgeries, as it highlights the increasing importance of understanding rare blood types.

What is CRIB?

• CRIB is a newly identified, extremely rare human blood group.
• It was discovered in a 38-year-old woman from Kolar, near Bengaluru, India, who is currently the only confirmed individual known to have this blood type worldwide.
• The name CRIB is derived from CR (representing the Cromer blood group system it is classified under) and IB (for India, Bengaluru, where the discovery occurred).
• Symbolically, CRIB also stands for “Chromosome Region Identified as Blood group,” highlighting its potential relevance in newborn and fetal medicine.
• It is classified under the INRA (Indian Rare Antigen) system, officially recognized by the International Society of Blood Transfusion (ISBT) in 2022.

Key Characteristics and Clinical Challenges of CRIB

• Uniqueness: CRIB falls outside the commonly known ABO and Rh systems. Its distinctiveness lies in the absence of a high-prevalence antigen that is present in most individuals.
• Panreactivity: The blood of the patient with CRIB exhibited panreactivity, meaning it reacted incompatibly with all known standard donor samples. This is a critical warning sign for an unknown blood group.
• Transfusion Difficulty: Due to the absence of the high-prevalence antigen, only CRIB-negative blood is compatible for transfusion, making suitable donors exceptionally rare. Even after testing 20 family members of the patient, no match was found.
• Antigen Source: The root cause was identified as a previously unknown antigen within the Cromer blood group system, which is associated with glycoproteins in red blood cell membranes. Until this discovery, no such variant had been documented.
• Antibody Development: Unlike typical scenarios where individuals develop antibodies against rare antigens due to pregnancy or previous transfusions, the patient with CRIB had never received a transfusion, yet her red blood cells reacted as if all donor blood was foreign and incompatible.
• Management of Emergencies: In the case of the index patient, doctors made the high-risk decision to perform cardiac surgery without a transfusion, which was carefully managed. This highlights the extreme challenges posed by such rare blood types.

Clinical Significance and Implications for Practice

• Transfusion Safety: The identification of CRIB enhances global transfusion safety and improves compatibility testing, especially in emergency transfusions and complex surgeries. For patients with CRIB, standard blood transfusions are not possible, posing critical risks during surgeries, pregnancies, or accidents without a compatible rare blood match.
• Prenatal Diagnostics: Early detection of CRIB can significantly help in managing cases of Hemolytic Disease of the Fetus and Newborn (HDFN) and prevent serious complications during pregnancy.
• Organ Transplants: This breakthrough also has positive implications for organ transplant compatibility.
• Rare Donor Registries: This discovery underscores the critical importance of establishing and maintaining rare donor databases and registries. The Rotary Bangalore TTK Blood Centre has already established a Rare Donor Registry in partnership with relevant organizations.
• Advancing Immunohematology: The identification of CRIB reinforces India’s significant contribution to rare blood group research and positions the nation as a key player in global immunohematology. Continued innovation in blood science, enhanced diagnostic tools, and international collaboration are vital for improving outcomes for patients with rare blood groups worldwide.

Already Existing Rare Blood Group Types

Globally, a blood type is considered rare if it affects one in every 1,000 people. The International Society of Blood Transfusion (ISBT) maintains a database of rare blood types and donors, emphasizing the importance of international cooperation to keep these databases updated and relevant.

Examples of already known rare blood types that lack common antigens include:

• Rhhull (Rh null): This is an extremely rare blood type where individuals lack all Rh antigens.
• Bombay (Oh): This rare blood group is characterized by the absence of H antigen on red blood cells, which is a precursor to A and B antigens.
• Jr(a-): Another example of a rare blood type lacking a specific antigen.
• In b negative: The Rotary Bangalore TTK Blood Centre has previously supported multiple rare blood type cases, including In b negative, which have been documented and presented internationally.

For patients with these existing rare blood types, a patient’s family is more likely to share the same rare blood type than random donors. These rare blood types pose significant medical challenges, including:

• No compatible donor found: Similar to CRIB, finding compatible blood for these patients is exceptionally difficult.
• Inability to receive standard blood transfusions: In emergencies, these patients cannot receive standard blood transfusions.
• Critical risks in specific medical scenarios: Pregnancy, surgeries, or accidents may pose critical risks without a rare blood match.

Understanding and preparing for the challenges presented by CRIB and other existing rare blood groups is paramount for medical professionals to ensure patient safety and effective treatment in all critical care scenarios.