The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. 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 A count of the T cells may be helpful in the diagnosis of immunodeficiency diseases and lymphocytic diseases. It is also used to monitor the response to therapy for these type of diseases.
Lymphocytes are white blood cells that are part of the immune system.