Tissue Type Test
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 HLA typing. Antigens can tell the difference between normal body tissue or foreign tissue (for example, tissue from another person's body). Tissue type helps find the best match for tissues or blood cells (such as platelets ). In some cases, a tissue type test may be done to see whether a person has a chance for developing 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 (inherited) the mother and half from the father. Identical twins have the same pattern, but everyone else has his or her 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 be successful.
- The more similar the antigen patterns are from two people, the more likely it is that they 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.
Two main antigen groups are used for a tissue type test. Class I has three classes of antigens (HLA-A, HLA-B, HLA-C) that are found on some kinds of blood cells. Class II has one class of antigens (HLA-D) that are found only on certain cells in the body. There are many different types of antigens in each category.
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 antigen patterns are most likely to be similar when the donated organ or tissue comes from a close relative of the person.
- See how likely two people are related. If the antigen patterns are very similar, they are likely to be related. But a tissue type can't prove definitively that two people are related. A tissue type test may be done as part of a paternity test to check to see if a man could be the father of a child.
- Find people who may have a high chance of certain autoimmune diseases.
How To Prepare
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 behaviors, 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
The health professional drawing blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure on the site and then put on a bandage.
How It Feels
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
- You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
- In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
- Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (such as Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.
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.
- For organ or tissue transplants, the results of tissue type 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.
- To check family relationships, the more alike the antigen patterns are, the more likely it is that the two people are related.
- If an antigen related to a disease is found, that disease is likely to be present.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include having had a blood transfusion in the past 3 days.
What To Think About
- A tissue type test is more useful than a blood type to see if two people may be related. Although tissue type cannot prove that two people are related, it can show how likely it is that they are related. Tissue type may be done as part of a lawsuit when blood relation is an issue. For more information, see the topic Blood Type.
- A genetic test looks at a DNA sample for genes or to analyze the number, arrangement, and characteristics of the chromosomes.
- Having an antigen pattern that is linked with certain diseases does not mean that the disease is present or will definitely develop. Your doctor will talk to you about the chance for developing the disease.
- A person who wishes to be a possible tissue donor (such as a bone marrow donor) generally has a tissue type test. The person's antigen pattern is kept on file in a tissue donor bank and checked to see if it matches anyone needing a transplant.
- There are registries of people who have had tissue typing done and who offer to be donors to anyone in need.
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby?s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
|E. Gregory Thompson, MD - Internal Medicine|
|Joseph O'Donnell, MD - Hematology, Oncology|
|Last Revised||September 6, 2012|
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