Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal disorder in which patients experience complement-mediated hemolytic anemia, with or without hemogobinuria. It is often associated with Venous Thrombosis and cytopenias. The lack of CD55 (decay accelerating factor) and CD59 (membrane inhibitor of reactive lysis) in RBC membranes is responsible for unchecked complement activation and subsequent chronic hemolytic anemia with episodic exacerbation.[8,9]
Traditionally, the acid hemolysis (Ham test) and sucrose lysis tests were used for identifying where standard for diagnosing PNH. However flow cytometry is more reliable becasue Ham testi can be confounded by a recent transfusion. The complement sucrose hemolysis test is technically complex. Therefore, flow cytometry (FC) has become the “gold standard” for detecting and quantifying PNH clones.
Most flow cytometric methods use fluorescent-labeled monoclonal antibodies to detect various GPI-anchored surface antigens. Other reported techniques use a mutant variant of the bacterial toxin, aerolysin, that binds to GPI molecules. FC is considered the gold standard for detecting GPI-deficient blood cells. Traditionally, CD55 and CD59 are commonly used markers in the analysis of PNH but there are other methods as well that focus on other GPI-linked antigens.
Stephen J. Richards, David BarnettThe Role of Flow Cytometry in the Diagnosis of Paroxysmal Nocturnal Hemoglobinuria in the Clinical Laboratory
Clinics in Laboratory Medicine, Volume 27, Issue 3, Pages 577-590, 2007
Borowitz MJ, Craig FE, DiGiuseppe JA, Illingworth AJ, Rosse W, Sutherland DR, Wittwer CT, Richards SJ. Guidelines for the diagnosis and monitoring of paroxysmal nocturnal hemoglobinuria and related disorders by flow cytometry. Cytometry Part B 2010; 78B: 211–230.