T (thymus derived) lymphocyte count

What the risks are:

Risks associated with venipuncture are slight:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Note: This test is often performed on people with altered immune systems. Therefore, the risk for infection may be somewhat greater than when venipuncture is performed on a person with a normal immune system.

Special considerations:

This test can be affected by:

• stress
• surgery
• chemotherapy medications
• corticosteroids
• immunosuppressive medications
• X-rays

A flow cytometric measurement is more accurate than manual counts.

People with decreased T lymphocytes may not react to diagnostic skin tests.

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.