Concern over the safety of blood transfusions arises
However striking the Hong Kong Red Cross’s slogan “Give blood, save life” sounds, its message is often challenged by the rising risk of transmitting diseases through blood transfusion.
For years, there has been a growing concern of the possibility of contacting infections through blood donation. There have been cases of patients' catching fatal diseases such as AIDS and hepatitis B from blood transfusions.
Regarding the process and safety of blood transfusion, Dr. Liu Hing Wing of Hong Kong Red Cross Blood Transfusion Service said, “The blood is treated with great care, as human lives are involved.” Their precautions start with the selection of blood donors.
Under international covenants, blood donors must be healthy. Every time a donor comes to give blood, the first step is a series of questions about his or her health condition.
Donors should not have undergone surgery in the past few months or have visited countries where infectious diseases have prevailed. Nor should they have been taking medicine for a considerable period of time.
Recently donors have been asked whether they are homosexual, sexually promiscuous or intravenous drug users.
If any uncertainty arises, the donors are advised not to give blood.
Besides, donors will be given a form to fill in after the donations, in case they remember or find any health problem afterwards. By referring to the code number of their forms, their blood can be withheld from potential recipients until they call back.
This process is known as donor deferral or self exclusion. It aims at compensating for the inadequacy of blood testing.
Then comes to the process of getting blood from the donors. Both the safety of the donors and the blood should be taken care of at the same time.
According to Dr. Liu, donating blood involves hardly any danger generally.
Nurses in the Red Cross receive professional training to carry out the operation. The equipment used is up to standard. Also, the speed of blood flow is carefully calculated. The amount of blood taken out is proportional to the donor’s weight.
“Normally,” said Dr. Liu, “problems associated with blood donation are rare. What a blood donor may get is a little bruise. There has been no significant accident so far.
“If this did happen, I think the press had already blown it up.”
After the blood is taken out from the donors, it is sterilized to keep safe for use.
Said Dr. Liu: “The sterilization process is similar to that for surgery. However, no matter how well it is done, it does not guarantee that all the bacteria is killed because every bag of blood is unique. “Apart from sterilization, the greatest achievement for the past 20 years is the close-system collection pack.”
This is used to keep the blood entirely protected from the outside world. From the time a needle is put into the donor’s skin, the blood will not have any contact with the air.
If the blood is not contaminated before it is taken from the donors, the treatment of the blood thereafter will introduce no bacteria or virus.
Different elements are then extracted from the blood and packed into bags within 24 hours because different elements require different treatment and have to be stored at different temperatures. Otherwise, they will easily decay.
After that, several samples are taken out for various chemical tests.
In order to match the samples accurately with the donors, the staff use computer bar codes for identification. To reduce errors, all tests are computerized.
“Not only bacteria and viruses are tested. Many aspects are also considered — for example, the blood type,” said Dr. Liu.
The process seems to be invulnerable. However, the loopholes lie in the tests.
Dr. Liu said, “Except for such diseases like syphilis and hepatitis B, which are tested for antigens, others are tested for antibodies. Examples are hepatitis C, HIV and HPLV-1, which is a newly discovered virus.
“The difference between antigens and antibodies is that with antigens, we can directly test a virus out.
“However, antigens cannot always be tested out. Let’s take AIDS as an example. When the antibodies come out, the antigens will disappear or hide away.
“The antigens may hide inside cells. They may become weaker when antibodies appear. They may also be insensitive to the test.
“Under these conditions, we turn to test for antibodies. Yet, antibodies do not appear immediately after a person is infected with the virus.
“It may take one or several weeks for generating antibodies. This time lag is called the window period.
“Therefore, theoretically, there is a chance that virus cannot be detected.
“The loophole may be the result of the testers’ insensitivity, testing errors or the window period.”
Dr. Liu said that the first two factors can basically be controlled.
“Most testers are now becoming more and more sensitive.
“The chance of testing errors is also very small because the testing procedure is very sophisticated. The problematic results will be tested twice more.
“If two out of three tests give positive results, then we will send it out for confirmation.”
However, the problem of the window period still remains.
Asked about the proportion of HIV carriers who have caught the disease from blood transfusion, r. Liu said, “Approximately among every 50,000 people, only one is found to be HIV positive.
“Taking this and the length of window period into account, the proportion of virus left unidentified is less than one in 1 million.
“HPLV-1 is similar. There is one positive out of every 30,000 to 40,000 people.
“The proportion of unidentified virus is the same as that of HIV and that for hepatitis B is smaller than one to 100,000.”
Besides the loophole that tests cannot screen out viruses, Dr. Liu brought out another problem.
“There are viruses that are not yet found or identified. It is even more difficult to estimate whether they will be transmitted through blood transfusion.
“The discovery of the virus is a rather recent development. Although the testers are consistently improved, they are still at the infant stage.”
The possible solutions to the problems are threefold. First, donors likely to have caught those diseases are excluded.
The second is to improve the testers by research and development in an effort to shorten the window period.
Third, technological research is used to devise and discover testers against new viruses.
Dr. Liu expressed his view about the public’s recent concern about the risk of transmitting AIDS to haemophiliacs and such kind of patients.
“After we have started to test for the virus since 1985, as far as I can remember, no such case occurred here.
“The risk that blood transfusion can transmit diseases always exists, though it is small. It is only after AIDS had become such an overwhelming issue that people’s concern over the safety of blood transfusion suddenly arise,” said Dr. Liu.
Every year, Hong Kong Red Cross receives 160,000 to 170,000 bags of blood from the citizens’ donation. The supply is just enough to meet the demand.
Unfortunately, for the past few years the supply has been decreasing, but the demand is expected to soar.
Mr. Au Man Kong, 26, who had just come out from the Hong Kong Red Cross Blood Donor Centre in Causeway Bay, said, “This is my second time to give blood. I have not thought of the risk of catching diseases from it.”
Dr. Liu believed the public’s anxiety over the safety of blood donation and blood transfusion did not impose a too obvious effect on the decreasing supply of blood. In fact, it seems that only a minority of people are worrying about the safety of giving blood.