Your doctor will diagnose lymphocytopenia based on your medical history, a physical exam, and test results.

A low lymphocyte count alone may not cause any signs or symptoms. Thus, the condition often is diagnosed during testing for other diseases or conditions.

Specialists Involved

Your primary care doctor may notice that you have unusual infections, repeat infections, and/or infections that won't go away. These infections may be signs of lymphocytopenia. Your primary care doctor may refer you to an infectious disease specialist to find out what's causing the infections.

You also may see a hematologist (blood disease specialist) or an immunologist (immune disorders specialist). Blood diseases and immune disorders can cause lymphocytopenia.

Medical History

To assess your risk for a low lymphocyte count, your doctor may ask:

  • About your risk for AIDS, including questions about blood transfusions, sexual partners, intravenous (IV) drug use, and exposure to infectious blood or bodily fluids at work
  • Whether you've ever had radiation or chemotherapy (treatments for cancer)
  • Whether you've ever been diagnosed with a blood disease or immune disorder, or whether you have a family history of such illnesses

Physical Exam

Your doctor will do a physical exam to look for signs of infection, such as fever. He or she may check your abdomen for signs of an enlarged spleen and your neck for signs of enlarged lymph nodes.

Your doctor also will look for signs and symptoms of diseases and conditions that can affect your lymphocyte count, such as AIDS and blood cancers.

Diagnostic Tests

Your doctor may recommend one or more of the following tests to help diagnose a low lymphocyte count.

Complete Blood Count With Differential

A complete blood count (CBC) measures many parts of your blood. The test checks the number of red blood cells, white blood cells, and platelets in your blood. The CBC will show whether you have a low number of white blood cells.

Lymphocytes account for 20 to 40 percent of all white blood cells. Although a CBC will show an overall low white blood cell count, it won't show whether the number of lymphocytes is low.

You may need a more detailed test, called a CBC with differential, to find out whether you have a low lymphocyte count. This test shows whether you have low levels of certain types of white blood cells, such as lymphocytes. The test results can help your doctor diagnose lymphocytopenia.

Flow Cytometry

Flow cytometry (si-TOM-eh-tree) looks at many types of blood cells. It's even more detailed than a CBC with differential. Flow cytometry can measure the levels of the different types of lymphocytes—T cells, B cells, and natural killer cells.

The test can help diagnose the underlying cause of lymphocytopenia. Some underlying conditions cause low levels of T cells. Others may cause low levels of B cells or natural killer cells.

Tests for Underlying Conditions

Many diseases and conditions can cause lymphocytopenia. Your doctor will want to find the cause of the disorder. You may be tested for HIV/AIDS, tuberculosis, blood diseases, and immune disorders.

Tests for these underlying conditions might include blood tests, bone marrow tests, and lymph node tests.

Lymph nodes are part of the immune system. They're found in many places in your body. During a physical exam, your doctor may find that certain lymph nodes are swollen. In lymphocytopenia, the lymph nodes may hold on to too many lymphocytes instead of releasing them into the bloodstream.

To test a lymph node, you may need to have it removed. Removing a lymph node involves minor surgery.

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Updated: December 30, 2013