| Subject | Contents |
| Definition | A test to measures the presence and amount of antibodies in blood against a particular type of tissue, cell, or substance. |
| Alternative Names | Titer - antibodies; Serum antibodies |
| How the test is performed | Blood is drawn from a vein ( venipuncture ), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding . |
| How to prepare for the test | No special preparation is necessary for this test. |
| How the test will feel | When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. |
| Why the test is performed | The antibody level in the blood is a reflection of the body's past experience or exposure to an antigen , or something that the body does not recognize as belonging to itself. The body uses antibodies to attack and eliminate the foreign matter. Every living cell has different protein markers on its surface. The body's immune system identifies those cells that are not part of itself by these surface proteins . Occasionally, the body makes an error and begins to recognize its own tissue as being non-self, or foreign. This leads to an immune response against that tissue type, cell, or substance that is part of the body. This is known as autoimmunity. Levels of antibodies in the blood (also known as the antibody titer) are measured to determine: the strength of an immune response to the body's own tissue in diseases such as SLE , and other autoimmune disorders . the need for a booster immunization, or if a recent administration caused a strong enough response from the immune system, bringing your antibody titer against a particular disease up to a preventative level. |
| Normal Values | This depends of the antibody being tested. If your health care provider is testing for antibodies against your own tissue, then the normal value would be zero or negative. If your health care provider is testing to see if your immunization brought your antibody titer up to a preventative level, then that would be a given value determined by that immunization. |
| What abnormal results mean | If your health care provider is testing for antibodies against your own tissue, abnormal results would show a positive antibody titer. This means that your immune system is fighting its own tissue, cells, or substances. If your health care provider is testing to see if your immunization brought your antibody titer up to a preventative level, an abnormal result would indicate that your body has not mounted an adequate response against the immunization, and you are not adequately protected from the disease. |
| What the risks are | Risks associated with venipuncture are slight: excessive bleedingfainting or feeling light-headed hematoma (blood accumulating under the skin) infection (a slight risk any time the skin is broken) multiple punctures to locate veins |
| Special considerations | Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. |
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