PNH signifies Paroxysmal nocturnal hemoglobinuria which is a clonal disorder of bone marrow stem cells which gives rise to blood cells that are unusually susceptible to activated complement. The manifestations of PNH include intravascular hemolysis, an increased risk of venous thrombosis, and associated hypoplastic anemia. Red blood cells in patients with PNH will hemolyze with acidified normal and acidified patient's serum, whereas normal RBC's will not hemolyze.
Ham’s test is an acidified serum test performed to diagnose PNH which includes intravascular hemolysis, an increased risk of venous thrombosis, and associated hypoplastic anemia. The Ham’s test is based on the tenet that complement will attach to RBCs at somewhat acid pH and that PNH RBCs are sensitive to complement fixation. Whole defibrinated blood collected in heparin is utilized.