All of the following are true of β thalassemia major, except –

Osmotic fragility test Red cells are suspended in a series of tubes containing hypotonic solutions of NaCl varying from .9% to 0.0% incubated at room temperature, for 30 minutes and centrifuged. The percent hemolysis in the supernatant solution is measured and plotted for each NaCl concentration. Cells that are more spherical, with a decreased surface/volume ratio have a limited capacity to expand in hypotonic solutons and lyse at a higher concentration of Nacl than do normal biconcave cells. These cells are said to have increased osmotic fragility and are seen in hereditary spherocytosis Conversely, cells that are hypochronic and flatter have a greater capacity to expand in hypotonic solutions, lyse at lower concentration, are said to have decreased osmotic fragility. These cells with increased surface/volume ratio are osmotically resistant and are seen in iron deficiency, thalassemia, liver disease and reticulocytosis.