The standard for diagnosing AIDS is the concentration of T4 white blood cells in the blood stream. When the number of these cells, which serve as disease-fighting agents, drops to 200 per cubic millimeter of blood, it signals the onset of the syndrome. (Ordinarily, people will range between 800 and 1200.)
愛滋病的診斷是以免疫作用的白血球 T4 細胞多寡為標準，低於二百才是所謂的「發病」（一般正常人在八百到一千二百之間）。