Ham test, also known as acidified hemolysis test, refers to the incubation of red blood cells in a weakly acidic environment to observe whether lysis and rupture of red blood cells occur after incubation, if there is lysis and rupture of red blood cells is a positive Ham test, a positive Ham test, which is commonly used in clinical practice for the diagnosis of paroxysmal sleep hemoglobinuria. Because this disease is a clonal disorder of hematopoietic stem cells, due to defects in the red blood cell membrane, it is very sensitive to complement, which is easily activated in an acidic environment, leading to lysis of red blood cells. Since the body stores a lot of carbon dioxide during nighttime sleep, resulting in an acidic environment, the body is prone to hemoglobinuria in the morning when urinating, and this disease is called paroxysmal sleep hemoglobinuria, and a positive Ham test is the confirmatory test for the diagnosis of paroxysmal sleep hemoglobinuria.