CD4 is a common test which may be used along with the test for CD8 cells to support the diagnosis of the body. It can be used with HIV viral load to assess the immune systems of the person diagnosed with the human immunodeficiency virus. Here the CD4 cells are white blood cells, which are called T Lymphocytes, or T cells, which can fight infection and play the important role in the function of the immune system. Therefore, the patient needs to check out the test to monitor the body condition via using this test. At the same time, the patient needs to control and follow the given instruction to get rid of this problem.