B and T cell screen

Alternative names 
Direct immunofluorescence; E-rosetting; T and B lymphocyte assays; B and T lymphocyte assays

A test that makes a quantitative measurement of T and B lymphocytes in the blood.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in air-tight vials or a syringe. During the procedure, the band 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.

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.

Normal Values
Values vary from laboratory to laboratory, and depend on testing technique, but typically, T cells comprise 68% to 75% of total lymphocytes and B cells 10% to 20%.

What abnormal results mean
Abnormal T and B cell counts suggest possible diseases. Further testing is indicated to confirm any of the suggested diagnosis.

An increased T cell count may suggest:

  • infectious mononucleosis  
  • multiple myeloma  
  • acute lymphoblastic leukemia

An increased B cell count may suggest:

  • chronic lymphocytic leukemia  
  • multiple myeloma  
  • Waldenstrom’s macroglobulinemia  
  • DiGeorge syndrome

A decreased T cell count may suggest:

  • congenital T-cell deficiency disease       o Nezelof syndrome       o DiGeorge syndrome       o Wiskott-Aldrich syndrome  
  • B cell proliferative disorders       o acquired immunodeficiency syndrome       o chronic lymphocytic leukemia       o Waldenstrom’s macroglobulinemia

A decreased B cell count may suggest:

  • acute lymphoblastic leukemia  
  • congenital immunoglobulin deficiency disorders  
  • acquired immunoglobulin deficiency disorders

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

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.

Johns Hopkins patient information

Last revised: December 6, 2012
by Dave R. Roger, M.D.

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