Which tests are traditionally associated with the diagnosis of paroxysmal nocturnal hemoglobinuria?

The sugar water test, sucrose hemolysis, and acidified serum test are key diagnostic tests for paroxysmal nocturnal hemoglobinuria (PNH). PNH is characterized by the destruction of red blood cells (hemolysis) due to a defect in the cell membrane, leading to an increased susceptibility to complement-mediated lysis.

The sugar water test is a simple screening test that identifies red blood cells that hemolyze in a solution with a low osmotic strength; the presence of hemolysis supports the diagnosis of PNH. Sucrose hemolysis assesses the ability of red blood cells to survive in a sucrose solution, where it exploits the cells' defenselessness against complement. The acidified serum test, also known as the Ham test, observes the hemolysis of red blood cells when mixed with serum at acidic pH, further confirming the sensitivity of these cells to complement.

These tests focus specifically on the hemolytic characteristics and susceptibility of red blood cells in PNH, distinguishing them from tests like the direct and indirect Coombs tests, which are used primarily for autoimmune hemolytic disorders, or tests like bone marrow aspiration, which evaluate hematopoiesis rather than hemolytic processes.