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Bombay blood group: Here’s why there is increased demand for this rare blood type

Ribhu Mishra
blood group, Bombay blood group

The 'Bombay blood group' - a rare blood type, has been at the centre of attention from the last two weeks in Mumbai’s healthcare scene. With scarce supply, the demand for the blood type has rocketed at Mumbai's hospitals.

What are the common and rare blood types?

The A, B, AB and O are the four most common blood groups. The 'Bombay blood group' was first discovered by Dr Y M Bhende in Mumbai, which was known as Bombay back then in 1952. The antigen over the surface of the Red Blood Cells helps in determining the group to which it belongs. The rare 'Bombay blood group', also known as the hh, is deficient in expressing antigen H. This means that the RBC has no antigen H.

To understand it better consider the AB blood group. In the aforementioned AB-blood group, both antigens A and B are present. A will have A antigens while B will have B antigens. In the case of the Bombay blood group 'hh', there are no A or B antigens.

Is it just rare in India or is it a globally rare blood group?

All around the globe, the instance of a human having a 'hh' blood type is one in four million. The incidence is higher in South Asia. While in India, one in 7,600 to 10,000 are born with this type.

The in-charge of Maharashtra State Blood Transfusion Council, Dr Arun Thorat states that this blood type is more common in South Asia than anywhere else in the world. The reason behind this is the inbreeding and close community marriages.

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'It is genetically passed' he said. Shared common ancestry among the people of India, Sri Lanka, Pakistan and Bangladesh is the main reason behind the elevated cases of hh blood phenotype in this region.

How is the testing for the Bombay blood group done?

An Antigen H blood test is required to test for hh blood. Generally, the 'hh' blood group is mistaken as the O group. The difference between them is that the O group has Antigen H, while the hh group does not.

The lack of Antigen H has nothing to do with the normal parameters of complete blood count (CBC). However, due to the rarity of the blood type, people face problems during a blood transfusion.

What are the transfusion limitations of the hh blood type?

According to a study in the Asian Journal of Transfusion Science published in 2015, it was observed that the individuals with hh blood group can only be transfused autologous blood or blood from another individual of the same Bombay hh phenotype type only. The occurrence of which is very rare. In case of transfusion with the A, B, AB or O, blood group rejection may occur. Also, hh blood group can donate their blood to ABO blood types.

Vinay Shetty of Think Foundation, an NGO said that an unofficial registry for Bombay blood group lists over 350 donors across India. But, only 30 active donors are available at a given instance. Also, the 'hh' group is generally not stored in blood banks. The reason behind it is mainly its short shelf-life ranging between 35 to 42 days and rarity of the blood type.

How the shortage occurred?

According to Vinay Shetty, the rise in demand is totally coincidental. Since last week, he has received as many as three requests from the hospitals in Mumbai for multiple hh blood type patients. Among these requests, two are cancer patients at Tata Memorial Hospital.

The rarity of this blood group could lead to the death of patients. In 2017, a cancer patient in Sri Lanka died for the want of hh blood group negative.