In Caribbean, labs only test for antibodies, not HIV virus
By Samantha Alleyne
August 12, 2002
Blood transfusion centres in the Caribbean test for the antibodies in the blood when testing for the HIV virus and not for the virus itself, according to head of the Caribbean Epidemiological Centre (CAREC), Dr James Hospedales.
Stabroek News contacted Dr Hospedales last week in Trinidad and asked about the standard of blood testing in relation to HIV, and the CAREC head said that there is no lab in the Caribbean that is equipped to test for antigen in the blood.
All the blood transfusion centres in this region test for the antibodies, which sometimes take as long as six months to be detected, and which will not be seen if the virus is in the window period.
Recently, the risk of contracting HIV from a blood transfusion, though slim as many of the experts say, captured the attention of the public after a five-year-old apparently contracted the virus from a blood transfusion she had at birth.
While it is not conclusively known if the child contracted the virus via the blood transfusion since the cause of the donor’s death is unknown, it was learnt that there is always a “slim” possibility that a person could be infected with the virus when having a transfusion.
Dr Hospedales told this newspaper that in 1989 all blood transfusion centres in the Caribbean put in place a screening process for prospective donors as well as testing for the antibodies in the blood.
During the screening process the prospective donors are asked to fill a questionnaire and they are questioned on several issues in order to determine whether or not they were put at risk of contracting the virus.
He conceded that there is a “small risk” involved of being infected when receiving the transfusion as the centres only test for the antibodies.
Pan American Health Organisation (PAHO) representative in Guyana, Dr Bernadette Theodore-Gandi, said that the centres in the Caribbean don’t have the technology to do antigen testing.
Asked whether her organisation would support having the technology installed at one lab in the Caribbean, preferably CAREC, the PAHO representative said that the centre has been going down that path.
The risk of being infected, which would more than likely scare persons who might have to receive blood, was pointed out to Dr Theodore-Gandi, who noted that a blood transfusion should only be used in a life and death situation.
“It should not be optional whether a person wants a blood transfusion or not, it should really be to save your life,” she said.
Further, she said, there are other diseases that a person could contract via the transfusion for which no testing is available.
She added that testing for the virus itself is mainly done in the USA and in some cases just for experiment and for research.
She feels that as the test becomes more available, eventually it will be done in the Caribbean.
According to information from the internet-based HIV/AIDS Resource Centre, during the acute period of infection, tests for the p24 antigen can detect HIV infection earlier than antibody tests. It said that the p24 antigen, the core structural protein of HIV, is detectable 2-3 weeks after HIV infection during the initial burst of virus replication. During this time, the blood of infected persons is highly infectious and tests for p24 antigen are usually positive.
On average, the p24 antigen is detected an estimated 6 days before antibody tests become positive. When antibodies to HIV become detectable, the p24 antigen is often no longer detectable because of antigen-antibody complexing.
The centre said that in August 1995, the Food and Drug Administration (FDA) in the USA recommended that all blood and plasma donations be screened for the p24 antigen, effective within 3 months of licensure of a test labelled for such use.
The FDA recommended p24 screening as an additional safety measure. One reason is that such testing would reduce the risk for HIV infection for persons who receive donated blood or blood products.
Among the 12 million annual blood donations in the United States, p24 antigen screening is expected to detect four to six infectious donations that would not be identified by other screening tests.