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A test that makes a quantitative measurement of T and B lymphocytes in the blood. Direct immunofluorescence; E-rosetting; T and B lymphocyte assays; B and T lymphocyte assays 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. Blood could also be obtained by capillary sample (fingerstick, or heelstick in infants). After the blood is drawn it goes through a two step process. First, the lymphocytes are separated from other blood elements. Once the cells are separated, identifiers are added to distinguish between T and B lymphocytes. The E-rosetting test identifies T cells and direct immunofluorescence is used to identify B cells. How to prepare for the test No alteration in diet is necessary for this test. Inform your health care provider of anything in your life that might affect your T and B cell count, such as: - X-rays
- chemotherapy
- surgery
- steroid therapy
- stress
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. What the risks are Risks associated with venipuncture are slight: - excessive bleeding
- fainting 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
Why the test is performed This test is performed to aid your health care provider in the diagnosis of immunodeficiency diseases. It may also be used to distinguish between benign and malignant lymphocytic disease. Finally, this test may be performed to monitor your response to therapy. 2011-06-28
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