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 parts. Once the cells are separated, identifiers are added to distinguish between T and B cells. The E-rosetting test identifies T cells and direct immunofluorescence is used to identify B cells.
How to Prepare for the Test
Tell your health care provider if you have had any of the following, which might affect your T and B cell count:
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
Your doctor may order this test if you have signs of certain diseases that weaken the immune system. It may also be used to distinguish between cancerous and noncancerous disease, especially cancers that involve the blood and bone marrow.
The test may also be used to determine how well treatment for certain conditions is working.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
Abnormal T and B cell counts suggest a possible disease. Further testing is needed to confirm a diagnosis.
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.
Other risks associated with having blood drawn are slight but may include:
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Soff GA, Green DL, Gardner LB. Hematologic manifestations of systemic disease: cancer. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hoffman Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:chap 157.
Daniel Levy, MD, PhD, Infectious Diseases, Lutherville Personal Physicians, Lutherville, MD, Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.