Ham test is done for -
Diagnosis of paroxysmal nocturnal hemoglobinuria

Until recently the diagnosis of P.N.H was based on special tests that were based on the principle that P.N.H red cells are susceptible to complement-mediated lysis. These tests are :

HAM Test

Ham's acidified serum test is one of the screening tests for P.N.H. Patient's red cells gets lysed in an acidic pH in the presence of complement.

Sucrose Test

Red cells lyse on the addition of sucrose and complement in the medium.
Addition of sucrose decreases the ionic strength.
But now the diagnosis of P.N.H depends upon analyzing the expression G.P.I—AP on the hematopoietic stem cells using monoclonal antibodies and flow cytometry. The simplest method is to analyze the expression of CD59 on erythrocytes.
PNH is diagnosed by flow cytometry, which provides a sensitive means for detecting red cells that are deficient in GPI-linked protein such as CD59.
PNH
Megaloblastic anemia
Sickle cell anemia
Thalassemia