Diagnosis: Paroxysmal Nocturnal Hemoglobinuria
• Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired stem cell disorder that leads to the production of abnormal red cells, white cells, and platelets.
• The red cell defect renders the cells more susceptible to complement-mediated hemolysis.
• The sucrose lysis test is a screening test for PNH; it is not used to make a definitive diagnosis.
• Sucrose provides a medium of low ionic strength that promotes the binding of complement to red cells.
• The acidified serum test used to be the gold standard for the diagnosis of PNH; it has been replaced by the flow cytometric measurement of CD55 and CD59 levels on red blood cells.
