TWO WIDELY-publicised cases of HIV transmission, allegedly through tainted blood, saw Dr. Lundie Richards, the National Blood Transfusion Service's director, coming out on the defensive. He says that the blood supply is safe.
"Our aim is to save lives not to cause problems and our records show that we have done very well. They also have these cases in the US, Britain, Australia. In sub-Saharan Africa, 30 per cent of transmission of HIV is through blood but I would not compare ourselves to the worst; the rate of transmissioin of HIV through blood in this country is miniscule, if the blood supply in the US, Cuba and so on, is safe then ours is safe and I can be challenged on that," he said.
But is the public being presented with complete information? Dr. Richards admits that there is a risky 'window period' that period between the day the blood donor becomes infected with a disease and when antibodies are produced, by the body as a result of the infection. Until the antibodies are produced current laboratory technology cannot detect infection in the blood.
In an infection such as Hepatitis C, for example, the window period is 60 to 90 days and for HIV infections, it is 21 to 28 days, using standard reagents and the ELISA test. So if a blood donor donates blood fewer than 28 days after the day he contracted the HIV, then the blood test will not be able to detect the disease. The risk is much greater for Hepatitis C with 60 to 90-day window period. However, according to Dr. Richards, the risk of transfusing tainted blood is very low in Jamaica.
"The level of risk for receiving tainted blood is low. It is less than one in 50,000 pints and when you consider that the bulk of blood donors do not fall in the low-risk pattern of behaviour then I think that it is very good. Between 1987, when we started testing for HIV, to now, there are fewer than eight cases, suggested to be HIV-positive from tainted blood and we have transfused more than one-half million units of blood during that 16-year period and this is a standard risk as compared to any other country using the standard, state-of-the art ELISA system," he stressed.
The ELISA test, widely used in medical laboratories is a rapid test, that links an antibody or antigen (virus or bacteria) to an enzyme. A match between an antibody and antigen points to a particular disease. There is currently a newer test -- the PCR (polymerase chain reaction) that cuts down the window period for HIV infections from 28 days to between 10 and 14 days but Dr. Richards says that it's not a cost-effective test to introduce in Jamaica.
"Look at Australia, they do 40,000 tests per year (using the PCR) and it costs US$12 to $14 million. ELISA is significantly less expensive, we can't compare the two and the efficacy to spend that amount of money to diagnose one or two tests, doesn't justify the money but because of the level of litigation in those countries (Canada, America, Australia), they do it. But even in European countries (PCR) is just catching on," he opines.
The PCR test works by picking up the actual genes of the virus and not the antibodies as is the case with the ELISA test. However, Dr. Richards said that unless the amount of the virus is at a high level, it will still not be detected by PCR. The tests may also be compromised if someone is on anti-retroviral drugs thus decreasing the virus load; if the person is in end-stage HIV/AIDS and lymphatic system if functioning at a low level affecting virus multiplication in the blood.
"The point is that it (the PCR) is not a test to replace ELISA, it is a complementary test because it can miss. (The germs) may not be detected using the PCR but ELISA focuses on the antibodies and the body takes time to produce antibodies. We are promoting healthy lifestyles, just like everybody else, and you can use that US$10 million to improve an entire population than one laboratory test that won't make a big difference. And questions are also raised in developed countries about (the PCR). Is it worth it to spend money on this test," he said.
So, until the scientists come up with more sensitive tests, whether using the ELISA or PCR tests, those taking blood transfusions must live with the dreaded window period.
PUT ASIDE DONATED BLOOD?
SINCE CURRENT blood tests cannot detect germs during the window period, some people have been asking, "well, why not put the donated blood aside until the window period has passed?"
Well, Dr. Lundie Richards says that the answer is that a virus such as the HIV requires someone's lymphoid tissue in order to multiply. The virus lies dormant in donated blood but once it is transfused, the virus makes use of the lymphoid tissue of that
person and starts multiplying again.
