EMA flow cytometry is a highly sensitive and specific screening test primarily used for the diagnosis of hereditary spherocytosis (HS).
It works by using a fluorescent dye, eosin-5-maleimide (EMA), which binds covalently to the red blood cell (RBC) membrane, specifically to the band 3 protein and Rh-related proteins. : EMA binds to the epsilon-NH2 group of lysine on band 3. In patients with HS, there is a reduction in these membrane proteins, leading to decreased fluorescence intensity when measured by a flow cytometer.
A lower mean fluorescence intensity (MFI) compared to healthy controls indicates a defect in the RBC membrane.
The test typically boasts a sensitivity of approximately 93–99% and a specificity of 95–99% for HS.
Beyond hereditary spherocytosis, the EMA binding test can also show reduced fluorescence in other RBC membrane disorders, including:
Hereditary Pyropoikilocytosis (HPP) Southeast Asian Ovalocytosis (SAO) Congenital Dyserythropoietic Anemia (CDA) Type II Hereditary Elliptocytosis (HE)
Key Advantages of test:
Speed: It is a rapid test compared to traditional methods like the osmotic fragility test
Requires only a small amount of blood, making it ideal for neonatal diagnosis.
It is less affected by factors like recent blood transfusions, or iron deficiency compared to older tests.
It cannot differentiate reliably among the various red cell membrane disorders.