Blood tests do not reveal whether a patient is infected with HIV or not. They are tests for white blood cells, red blood cells and platelets. During the acute phase of AIDS, some patients may show a transient decrease in white blood cells, lymphocytes, and platelets, but this change in blood count is not diagnostic of AIDS. In the asymptomatic phase, the majority of patients show a slow decline in lymphocytes, and when they enter the AIDS phase, their lymphocytes may drop to a very low level, even close to zero. Platelets can also be reduced due to severe infection in patients. To confirm whether a patient is infected with HIV, a blood test for antigens or antibodies should be done to confirm the diagnosis.