Using the eosin-5-maleimide binding test in the differential diagnosis of hereditary spherocytosis and hereditary pyropoikilocytosis.

Background: Flow cytometric analysis of eosin-5-maleimide (EMA)-labeled red blood cells (RBCs) has been used as a screening test for the diagnosis of patients with hereditary spherocytosis (HS). We assessed the fluorescence profiles for patients having HS and hereditary pyropoikilocytosis (HPP) together with their red cell indices.

Methods: Flow cytometry was used to analyze EMA-labeled RBCs. Membrane protein defects and spectrin variants were identified by SDS-polyacrylamide gel electrophoresis.

Results: An overlay of single fluorescence peaks for normal individuals, and those with HS and HPP revealed a graded fluorescence intensity (normal > HS > HPP). The area under each peak defined a specific RBC subpopulation; namely, normal RBCs, spherocytes, and microspherocytes. HS RBCs having a gross reduction in band 3 or spectrin content gave fluorescence readings almost as low as those for HPP. Complex fluorescence profiles were obtained for isolated HS and HPP cases.

Conclusions: The mean cell volume is a useful discriminator for HS and HPP. We presented evidence that a mixed RBC population could occur in some HS and HPP patients, either in a transient manner or for a long-term period. A differential diagnostic scheme for detecting HPP and HS by flow cytometry is proposed.