Tests we carry out on donated blood

Syphilis is caused by a bacterium called Treponema pallidum. This family of bacteria can also cause tropical diseases called Yaws and Pinta. Syphilis is usually a sexually transmitted infection which, if untreated, can cause serious disease. Yaws and Pinta cause skin and joint problems.

All three diseases are fully treatable with antibiotics. The tests we use look for specific antibodies to the bacterium. These antibodies remain in a person’s blood many years after the infection has gone.

A positive test for syphilis often relates to an infection in the past, but we are not able to use blood if the test is positive.

Hepatitis B virus (HBV) is one of several viruses that can cause inflammation of the liver (hepatitis), and sometimes liver damage.

Hepatitis B is very common in many parts of the world where it is often transmitted from mother to child at birth or in infancy. Most donors we identify have an association with these areas of the world and appear to have been infected since childhood or in early life.

We do three tests for the virus. One looks for a marker called hepatitis B surface antigen, which is part of the ‘coat’ of the virus. The second looks for the virus itself, targeting the virus nucleic acid. The third is an anti-core screening which will identify if the donor has had Hepatitis B previously. The third test was introduced from 31 May 2022. 

If we find surface antigen and/or the virus nucleic acid in a donor’s blood then further tests are performed to confirm the result. Many of the donors we identify have been infected with the virus for years and are completely well.

Sometimes we find a donor with new (acute) hepatitis B infection. Most adults who get hepatitis B have a short illness and overcome the infection.

Occasionally we get a positive result in our hepatitis B test because the donor has recently had an immunisation against hepatitis B and not because infection is present.

Human immunodeficiency virus (HIV), if untreated, affects the immune system with the development of Acquired Immune Deficiency Syndrome (AIDS). The HIV virus is transmitted sexually, can be passed from mother to baby, and by intravenous drug use.

Once an individual becomes infected with HIV, the virus remains in the body. A person who has HIV does not necessarily have AIDS. We perform two tests for the virus; one is a combination test that looks for both a protein in the virus coat and antibody to the virus; and a second that looks for the virus itself, targeting the virus nucleic acid.

If either or both of the tests are reactive, further tests are done to confirm the result. Unlike many other infections the antibodies produced do not protect against the virus.

Hepatitis C virus (HCV) like hepatitis B, infects the liver and can cause inflammation and liver damage. The virus is commonly transmitted by needles, and thus may be associated with injecting drug use. Like HIV, HCV can persist in the body even when antibodies are present.

We perform two tests for the virus, one that looks for antibody to the virus, and a second that looks for the virus itself, targeting the virus nucleic acid. If either or both of the tests are reactive, further tests are done to confirm the result.

Like HIV, the antibodies produced do not protect against the virus. Many of the donors we identify have had the virus for years and feel completely well.

Hepatitis E Virus (HEV) can infect both animals and humans. HEV infection usually causes no symptoms but if it does, it generally produces only a mild inflammation of the liver, hepatitis E.

Normally the virus infection will clear by itself. However, it is known that patients whose immune system is suppressed (e.g. chemotherapy or transplant patients) cannot clear the virus themselves and most will develop a persistent infection which may lead to chronic inflammation of the liver.

You will be informed if the virus is found in your donation, even though it will be short-lived, in case you start developing any signs of illness.

Your first donation, and some selected future donations, are tested for Human T-lymphotropic Virus (HTLV) - a virus that infects certain white blood cells known as T-lymphocytes.

Like HIV, once a person is infected, the virus remains in the body even after antibodies develop. Most people with HTLV infection remain completely well and never experience any illness. Occasionally, the virus can cause a neurological condition called Tropical Spastic Paraparesis (also known as HTLV-associated Myelopathy), or a blood disorder called Adult T-cell Leukaemia. These conditions are very rare.

HTLV infection is found more often in people from Japan, the West Indies, and parts of the Middle East. It is most commonly transmitted from mother to child through breastfeeding but can also be spread through sexual contact or intravenous drug use. We routinely screen donations for antibodies to HTLV.

If a test result is reactive, further confirmatory testing is performed.

Hepatitis A (HAV) is a virus that primarily affects the liver. It is usually spread by contaminated food or water, known as faecal-oral transmission, but may be spread within households or by infectious food workers. In rare cases hepatitis A may be passed on through blood transfusion.

In most healthy adults, Hepatitis A causes a short-term illness with symptoms such as fatigue, nausea, abdominal pain, or jaundice (yellowing of the skin or eyes). However, in some cases, especially in older adults or those with pre-existing liver conditions, the infection can be more serious.

Although Hepatitis A does not lead to long-term (chronic) infection like some other hepatitis viruses, it can still be transmitted through blood. Patients who receive transfusions may be more vulnerable to complications, so it is essential that we identify and remove any donations that may carry the virus.

Parvovirus (B19) is a small DNA virus that commonly infects humans. Many people are exposed during childhood or early adulthood, often without serious symptoms. The infection caused by Parvovirus B19 is also called slapped cheek syndrome or fifth disease.

In healthy individuals, the infection usually causes only mild illness, such as flulike symptoms or a temporary rash, and many people may not realise they have been infected. However, for certain groups of patients, Parvovirus B19 can cause significant health problems. This includes individuals with weakened immune systems, people with certain blood disorders (such as sickle cell disease or thalassemia), and pregnant women, where infection can pose risks to the unborn baby.

All donations from plasma donors and whole blood donors are routinely screened for hepatitis A and parvovirus B19.

Malaria is caused by parasites which are transmitted by the bites of mosquitoes. The infection causes fever and is a major cause of death in some parts of the world. We test for antibodies to the malaria parasites. A confirmed positive result does not necessarily mean that the individual has active malaria, merely that they have had malaria at some time.

T-cruzi is a parasite called Trypanosoma cruzi, found in certain parts of Central and South America. It is transmitted to humans by biting insects or from mother to baby at the time of birth, or by blood transfusion.

Over many years, the parasite can cause damage to the muscles in the heart and intestines, leading to an illness called Chagas disease. Not all infected people become ill. Our tests look for antibodies to the infection. A donor’s place of birth and travel history determine whether the test is required.

West Nile Virus (WNV) is an infection transmitted by the bites of mosquitoes. It most often causes a mild ‘flu-like’ illness, but can also cause a more serious illness, especially in the elderly and in those with a suppressed immune system. It can be transmitted by blood transfusion from a donor who has recently been infected.

WNV is commonly found in Africa, Western Asia, Europe, Australia, USA and Canada. The ‘season’ for this virus is between 1st May and 30th November.

If you have visited an area where WNV is circulating, or tell us that you have previously been diagnosed with the virus, we may test your donation to make sure that your donation is free from any possible infection. We will inform you if your test shows any sign of infection.

Cytomegalovirus (CMV) is a very common virus which causes a mild ‘flu-like’ illness. Individuals in good health make a full recovery and are usually unaware of the infection. We may test for antibodies against the virus.

A positive test indicates that the individual has had CMV infection and may still have the virus. Having antibodies to CMV is of no significance to the health of the donor. However, for patients with a poor immune system (bone marrow recipients or small babies), CMV can cause a life-threatening illness. CMV-positive blood is safe for most patients, and donors are not informed of a positive result.