Even as many government run blood banks have come under scanner for irregularities in complying with guidelines of National Blood Transfusion Council (NBTC) in terms of collection, storage and pricing of blood, blood banks across the state have also been found negligent towards saving the rarest of rare Bombay blood group or hh-type blood. The state today has 303 blood banks and 3 cord blood banks.

The magnitude of the lapse can be gauged from the fact that the group is so rare that it is found only in about 0.0004 per cent of the population, or in about 4 people per million individuals. A special anti-H antiserum is used to determine whether a blood sample is of this type.

Experts inform that a rare genotype (blood group) of people was detected in Mumbai, a few decades back, who neither had A, AB, B or O group. This rare genotype was labelled as the Bombay blood group. If a Bombay blood group recipient is not transfused the blood of a Bombay blood group person, it can lead to a haemolytic transfusion reaction, which can be fatal and lead to death.

Studies reveal that this is due to the absence of the H substance (antigen) in the red cells. The absence of the H substance is attributed to the deficiency of the enzyme fucosyl transferase. The Bombay blood group phenotypes lack H antigen in the red cells and have anti-H in the serum.

Says a blood bank expert, “Family studies have shown that the Bombay phenotype, called as Oh, is due to the presence in homozygous state of a rare recessive gene.”

The precursor protein from which the blood group proteins are formed is termed as the H substance. This is bio-chemically produced by the binding of Fucose to the surface glycoproteins, the process being catalysed by Fucosyl transferase. If N-acetyl galactosamine binds to the H substance, it forms the blood group A, whereas if galactose binds to it, it forms the group B. Absence of any binding substance produces the O blood group.

Studies reveal that all human red blood cells with exceedingly rare exceptions carry the red cell H antigen. It is present in greatest amount on type O red cells and least on type A1B cells. The H antigen is an intermediate stage in the production of the A and B antigens. The individuals with the so-called Bombay phenotype are recognised with the presence of anti-H in the serum, in addition to anti-A and anti-B, as in type O persons.

Experts say that if proper blood grouping or testing practices is not followed, it can lead to people with Bombay blood group not being detected. Other issues related to Bombay blood group is that blood is incompatible with all A, B and O donors. In routine forward grouping, this blood group would give reaction as an ’O’ blood group where as in serum grouping it would show reaction with ’O’ cells due to the presence of anti H in their serum.

Experts advocate that since Bombay blood group is the rarest of the rare group, it is desirable to develop cryopreservation facilities for rare donor units. Every blood bank can easily maintain a rare blood type donor file from amongst their regular voluntary donors.

“If these blood banks can borrow or exchange rare blood units in times of need, a lot of problems related to rare blood groups like Bombay blood group can be solved. This is only possible if each blood bank has a large number of committed regular voluntary donors,” the expert concluded.