Donated blood may be unsafe even after test.

[Guest guest]

New Delhi: Donated blood being transfused into you may not be entirely safe,

even after it has undergone the present- day gold standard test. This has

now been confirmed by an AIIMS study.

After studying 5818 donated blood samples that tested safe through ELISA ,

AIIMS department of transfusion medicines ran the samples through the Nucleic

Acid Testing (NAT) and found five samples to contain Hepatitis B and Hep c

virus.

This probably saved the lives of 15 people who could have got transfused with

the infected blood.

Faculty in charge of the AIIMS blood bank Dr.Kabita Chatterjee, who conducted

the 'Novartis Diagnostic NAT study ', told TOI, " ELISA is not foolproof against

transfusion transmitted infections like HIV and hepatitis. With ELISA known to

give false negatives, it is better to use NAT as an additional layer of safety "

A study at AIIMS has found that blood the hospital took from donors after

testing it for infections might not have been entirely safe. Now to ensure zero-

risk transfusion, the hospital is testing blood samples of patiens through

Nucleic Acid Testing (NAT) free of charge.

" We divide whole blood samples into three components- red blood cells, platelets

and plasma. Because five samples were found to be infected even after ELIS

confirmed them as safe, 15 people got saved. The infected donors were then sent

for counselling, thereby ensuring they don't continue infecting others

unknowingly,' said Dr. Kabita Chaterjee, facility in charge of AIIMS' blood

bank.

Experts said ELISA testing method is based on serological tests that look for

antigen (a part of the infectious agent that has invaded the body) or the

antibody (a typs of protein that are produced against the antigens).

These markers take some time to appear in the body after infection occurs.

During this period (window period), the infectious agent continues to multiply

and any blood donated in that period will transmit the infection to the

recipient of blood.

According to Dr. Debhasish Gupta, national programme officer of blood safety at

NACO, several private hospital use NAT which is sensitive enough to identify

samples that contained viral genetic material during the window period- the

length of time after infection that it takes to detect antigens of the virus or

for a person to develop specifec antibodies to be detected by current testing.

Dr. Gupta said, " HIV transmission through blood is 1.1 % of all HIV cases.

Nearly 10 million units are used for transfusion every year. "

Dr. Chatterjee said NAT could further reduce the window period for donor blood.

While the window period for Hep B and Hep c was reduced from 120 days to 30 days

when tested under NAT, the window period for HIV fell from 2-6 years to just 5

days. But unlike ELISA which costs around Rs. 100, NAT costs 10 times more.

" NAT amplifies the genetic material of the viruses multifold in a very short

period. This amplifies even very low amounts of genetic material that cannot be

identified otherwise, " Dr. Chatterjee said.

During the AIIMS study, 5818 samples were tested and five were found to be

infected when tested through NAT - four were Hep B and one Hep C positive.

Several other government run hospitals in Delhi like Raqm Manohar Lohia Hospital

will introduce NAT soon, said senior health officials.

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