WHO world blood donor day 2014

14 June each year is the World Health Organization (WHO) world blood donor day. Blood donation is essential to save the lives and/or improve the health of many patients.

John Frater

Dr John Frater is a MRC Senior Clinical Fellow in the Experimental Medicine Division and a practicing clinician in acute medicine. His main research interest is trying to eradicate HIV.

NDM spoke to Dr Frater about the importance of blood donation and why in the UK we screen all donated blood for diseases such as HIV.

Q: Why should more people donate blood?

John Frater: Donating blood can help many people in many different ways. Most people think of accidents and emergency operations as the main use for donated blood. While this is true, blood is also needed for many patients with chronic long-standing conditions. Blood has many different components, which can be separated out to help different people with different problems. For example, platelets can be used to help people with blood clotting problems, and plasma can be used to provide proteins and other factors that can help to reverse clotting problems or assist the immune system. Depending on what the donor wants to contribute, the process of giving blood can be fine-tuned so that certain components are removed whilst others are left behind – for example platelets can be donated on their own without taking red cells or plasma.

Blood and its components are always in demand, so the more people who come forward to donate the better – 8,000 units are needed every day in the UK. Stocks of blood fluctuate, but there is usually around 4-10 days’ worth of blood available, depending on the blood type that is needed. In order to maintain these stocks a regular supply of donors is required.

The NHS Blood and Transplant website is an excellent place to find out more information about becoming a donor.

immunology

Q: Why are there some restrictions on donating blood?

JF: Blood transfusions have a very interesting history and over the years the process has become increasingly safe. The story behind transfusions dates back nearly 400 years to British scientists in the 17th century when William Harvey first discovered that our blood circulates around the body, and then Richard Lower successfully transfused blood from one dog to another.

Successful transfusion of blood to humans was first carried out by another British physician, James Blundell, in 1818 but it remained a dangerous process. A major breakthrough which allowed transfusions to be given much more safely was the discovery of blood groups (known as A, B ,O and AB) by an Austrian physician, Karl Landsteiner, in 1900 which meant that donors and recipients could be matched to reduce the chance of the patient having a reaction to the transfusion.

However in the 20th century it became apparent that certain infections could be transmitted through blood donations and blood has been routinely tested for HIV since 1986 and the Hepatitis C virus since 1991.

To reduce the chance of blood-borne viruses and infections getting into the blood-bank supply certain rules are applied over who can donate. Most people can give blood, but not if they have been at risk of acquiring certain infections. So, for example, one cannot donate if known to be infected with viruses such as HIV, Hepatitis C or Human T-Lymphotropic virus (HTLV). Individuals who have had a blood transfusion since 1980 are also not allowed to donate. Other exclusions include people who have injected themselves with drugs, who have had sex in countries where HIV is common, men who have sex with men, or women who have had sex with a man who has had sex with other men.

There are a number of other exclusions which between them are designed to either ensure that the donor comes to no harm by donating blood and to make sure that any donated blood products are safe for transfusion. There is a 24 hour telephone line (0300 1232323) provided by the NHS to clarify issues or provide further details.

Q: What diseases is donated blood tested for?

JF: Blood is tested for infections that can be transmitted by transfusion. These include viruses such as HIV, Hepatitis C and HTLV and the bacteria that causes syphilis. These tests are carried out on all blood donated in the UK. Other tests are carried out on certain blood donations where they are deemed necessary – these might include tests for malaria, cytomegalovirus or West Nile virus – if the donors are thought to be at increased risk of exposure to these infections.

Donating blood should never be used as an alternative method for testing oneself for infections such as HIV. If a person thinks they may have been exposed to HIV, it is critical that they attend their GP or a local sexual health clinic so that pre-test counseling can be undertaken and tests can be tailored to the individual. This is particularly true for recent exposures, as there is a window period after transmission of HIV of around 6-12 weeks before standard tests become positive, and different tests would need to be carried out.

Q: Why is it important to refrain from giving blood if you think that you might be HIV positive?

JF: HIV can spread through blood transfusions, as can all the infections described above. This is especially true if an HIV positive donor is not receiving antiretroviral therapy to treat the infection. Without therapy, the levels of HIV in the blood are much higher, making transmission more likely. Interestingly, if an HIV positive person is being successfully treated with antiretroviral therapy the risk of transmission through sex is incredibly small. However, with blood transfusions, cells are passed from one person to the next (this doesn’t happen with sexual transmission) and therefore there is still a theoretical risk of transmission even if the donor is receiving therapy. For this reason, being HIV positive is one of the restrictions on giving blood.