tissue type test

test overview

a tissue type test is a blood test that identifies substances called antigens on the surface of body cells and tissues. checking the antigens can tell if donor tissue is safe (compatible) for transplant to another person. this test may also be called human leukocyte antigen (hla) typing. based on the antigens, the immune system can tell the difference between normal body tissue and foreign tissue (such as tissue from another person's body). tissue type helps find the best match for tissues or platelets). in some cases, a tissue type test may be done to see if a person has a chance of getting certain diseases that cause the body to attack its own cells, such as autoimmune diseases.

a special pattern of antigens (called tissue type) is present on each person's cells and tissues. half of each person's antigens come from (are inherited from) the mother and half from the father. identical twins have the same pattern, but everyone else has their own special pattern. brothers and sisters have a 1-in-4 chance of having an identical match. each person's antigen pattern can be "fingerprinted" through a tissue type test.

• the closer the match of antigens, the more likely that an organ or tissue transplant will succeed. a better match may mean that fewer anti-rejection drugs will be needed.
• the more similar the antigen patterns are from two people, the more likely it is that those people are related.
• some diseases (such as multiple sclerosis or ankylosing spondylitis) are more common in people who have certain antigen patterns. the reason for this is unknown.

why it is done

a tissue type test is done to:

• see if the antigen pattern for donated tissue or organs (including a blood platelet transfusion or bone marrow transplant) is a match. the success of a transplant depends on how closely the antigen patterns match. the patterns are most likely to be similar when the donated organ or tissue comes from a close relative of the person.
• find people who may have a high chance of certain autoimmune diseases.

how to prepare

in general, there's nothing you have to do before this test, unless your doctor tells you to.

if you are donating tissue or blood cells, your doctor may want to talk about your medical history—such as a history of cancer, infections, high-risk behaviours, use of drugs, exposure to toxins, and foreign travel. this may be important in understanding whether your donor tissue can be used.

how it is done

a health professional uses a needle to take a blood sample, usually from the arm.

how it feels

when a blood sample is taken, you may feel nothing at all from the needle. or you might feel a quick sting or pinch.

risks

there is very little chance of having a problem from this test. when a blood sample is taken, a small bruise may form at the site.

results

• for organ or tissue transplants, the results of tissue type tests show whether the donated tissue matches. the antigen pattern match is different for each type of transplant. for example, the match for a bone marrow transplant needs to be closer than the match needed for a kidney transplant.
• if an antigen related to a disease is found, that disease is likely to be present.