In a first-of-its-kind global breakthrough, Indian scientists have identified a previously unknown human blood group, named 'CRIB', after a routine heart surgery case in Karnataka’s Kolar district took an unexpected turn.
The discovery was made when a 38-year-old woman, admitted for cardiac surgery, was found to be incompatible with all available units of O+ blood -- the most common blood type. Despite her blood being typed as O+, doctors were alarmed when none of the standard O+ units matched her profile.
The case was referred to the Rotary Bangalore TTK Blood Centre, where experts launched a months-long investigation involving advanced serological testing and family blood analysis.
“This case presented as panreactive; the patient’s blood was incompatible with all standard test samples,” said Ankit Mathur, Medical Director of the centre.
The woman’s blood was tested against 20 of her family members, yet not a single donor was found to be compatible.
"We suspected the presence of an extremely rare or previously unidentified antigen,” Mathur added. Samples were sent to the International Blood Group Reference Laboratory (IBGRL) in Bristol, UK. After 10 months of extensive molecular testing, IBGRL confirmed the presence of a new antigen -- officially categorised under the Cromer blood group system and named 'CRIB', an acronym that also nods to its origin in Bengaluru, India.
The finding was announced at the 35th Regional Congress of the International Society of Blood Transfusion (ISBT) in Milan, Italy, in June 2025. The woman is now recognised as the first known individual in the world to carry this antigen.
Given the extreme incompatibility with existing blood supplies, doctors successfully performed the woman’s heart surgery without a blood transfusion—an achievement made possible through meticulous coordination between the surgical team and her family.
“This is a proud moment for Indian transfusion science,” said Mathur, adding, “The CRIB antigen discovery demonstrates the value of building scientific capacity and maintaining long-term collaboration with international reference laboratories.”
In response to the discovery, the Rotary Bangalore TTK Blood Centre has launched a Rare Donor Registry in partnership with the Karnataka State Blood Transfusion Council, IIH-ICMR Mumbai, and the International Society of Blood Transfusion. The aim is to prepare for rare cases like this and build a global database of rare blood types.
The centre has previously contributed to the identification of several rare blood types, including D- -, Rh null, and Inb-negative, further cementing its status as a leader in advanced transfusion science.
“While the CRIB discovery marks a milestone in medical science, it also underscores a critical challenge. As the woman is the only person known to have this blood type, finding a compatible donor in the future will be extraordinarily difficult,” said Mathur, adding, “This case highlights the urgent need for deeper, sustained research in blood group science and the expansion of rare donor registries globally.”
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