Hereditary spherocytosis with normal osmotic fragility after incubation. Is the autohemolysis test really obsolete?

Two patients in two families had hereditary spherocytosis but lacked a population of RBCs with increased osmotic fragility after incubation. The diagnosis in each patient was confirmed by the presence of splenomegaly, spherocytosis, reticulocytosis, and abnormal autohemolysis corrected by glucose. Sodium flux studies showed increased sodium permeability of the RBC membrane in one patient and normal permeability in another. Hereditary spherocytosis was also present in three other family members of patient 2. The autohemolysis test is of value in confirming the diagnosis in patients with hereditary spherocytosis and normal incubated osmotic fragility.