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Platelet associated antibodies |
| Definition: |
| This is a test to identify the presence of abnormal antiplatelet antibodies in plasma. |
| How the test is performed: |
| Adult or child: 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. Infant or young child: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding. |
| How to prepare for the test: |
| Adults: No special preparation is necessary. Infants and children: The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
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| 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: |
| This test may be ordered when the person has a low platelet count (thrombocytopenia). It is used to detect antibodies against platelets. |
| Normal Values: |
| A negative test is normal. |
| What abnormal results mean: |
| Antiplatelet antibodies are present. Antiplatelet antibodies are antibodies that bind to platelets, and may result in increased platelet destruction. This causes a low platelet count (thrombocytopenia), and may be associated with bleeding. These antibodies may be associated with idiopathic thrombocytopenic purpura (ITP) or drug-induced thrombocytopenia (caused by heparin or other drugs). In some cases, ITP antibodies arise for unknown reasons. In the drug-induced types, presumably drugs associate with normal proteins on the surface of platelets and modify their structure in such a way that they appear to the immune system as abnormal proteins. The antibodies may be either IgM or IgG type. |
| What the risks are: |
| Special considerations: |
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With current testing methods, false positive and false negative results are common. Therefore, ITP is usually a clinical diagnosis, as this test is unable to reliably rule in or out immune causes for thrombocytopenia (low platelets). 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. |
Reviewed By: Rebecca Elstrom, M.D., Division of Hematology-Oncology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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