Ham's (Acid Hemolysin) Test
Alternate Names : Ham Test
DefinitionThe Ham's (acid hemolysin) test looks for increased fragility of red blood cells in mild acid.
Why is the Test Performed?
This test is used to confirm the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH).
Diagnosis of PNH can be confirmed by having a positive acidified serum test (Ham test). In acidified serum, complement is activated by the alternate pathway. It binds to red blood cells, and ruptures the abnormal PNH cells, which are unusually susceptible to complement. With newer methods of diagnosis, such as flow cytometry, this test has become less important in the diagnosis of PNH.
The Ham test is also positive in another rare disorder called congenital dyserythropoietic anemia, but in this case the sugar-water fragility test is negative. Furthermore, the clinical aspects of this disorder are not similar to PNH.
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