When the scientific community discovered that human immunodeficiency virus (HIV) attacks and destroys T-helper cells, physicians began monitoring this cell population in affected patients. Flow cytometric analysis helps determine the absolute T-helper cell counts in a patient blood sample.
A patient that is infected with HIV is considered HIV-positive until the absolute T-helper cell count crosses a threshold of 200 cells/mm3. After the T-helper cell count falls below this threshold, the patient's physician may change the diagnosis to acquired immunodeficiency syndrome (AIDS).
