Hereditary Spherocytosis o RBC band 3 protein testing is a very sensitive and Indications for Ordering specific test for the diagnosis of hereditary Use to confirm diagnosis of hereditary spherocytosis when spherocytosis hemolytic anemia and spherocytes are present Physiology • RBC band 3 protein is a major structural protein of RBCs Test Description o Reduction in the amount of band 3 fluorescence after Test Methodology binding with EMA correlates with spherocytosis • Red blood cell (RBC) surface protein band 3 staining with Genetics eosin-5-maleimide (EMA) analyzed by flow cytometry Clinical Validation Genes: ANK1, EPB42, SLC4A1, SPTA1, SPTB • Validated against the clinical diagnosis of hereditary Inheritance spherocytosis supported by osmotic fragility and/or • Autosomal dominant: 75% molecular testing • Autosomal recessive: 25% Tests to Consider Penetrance: variable Structure/Function Primary Test • Chromosomal location: 17q21.31 RBC Band 3 Protein Reduction in Hereditary Spherocytosis • Provides structure for the red cell cytoskeleton 2008460 • Use to confirm diagnosis of hereditary spherocytosis Test Interpretation when hemolytic anemia and spherocytes are present Sensitivity/Specificity Related Test • Clinical sensitivity: 93% Osmotic Fragility, Erythrocyte 2002257 • Analytical sensitivity/specificity: unknown • Functional testing of RBC sensitivity to osmotic stress Results Disease Overview • Normal o Normal staining of band 3 protein with EMA does not Prevalence: 1/2,000 in northern Europeans suggest hereditary spherocytosis Symptoms • Abnormal • Hemolytic anemia o Decreased staining of band 3 protein with EMA provides o Pallor evidence for hereditary spherocytosis o Fatigue o Three rare disorders may be associated with a positive o Jaundice result for this test o Splenomegaly ▪ Congenital dyserythropoietic anemia type 2 • Kernicterus ▪ Southeast Asian ovalocytosis • Pigmented gallstones ▪ Hereditary pyropoikilocytosis • Equivocal Diagnostic Issues o Unclear whether the level of band 3 protein staining is • Depending on severity of symptoms, diagnosis of normal hereditary spherocytosis can rule out other causes of o Insufficient evidence to support or negate a diagnosis of hemolytic anemia hereditary spherocytosis o Examination of a peripheral blood smear is a quick and easy initial screen Limitations o Osmotic fragility can confirm compromised integrity to Not typically used as a screening test, but has been proposed osmotic stress as a screening test by many authorities

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