All of the following are true of 3 thalassemia major, except-

Ans. is 'd' i.e. increased osmotic fragility Osmotic fragility test o Red cells are suspended in a series of tubes containing hypotonic solutions of NaC1 varying from .9% to 0.0% incubated at room temperature, for 30 minutes and centrifuged. o The percent hemolysis in the supernatant solution is measured and plotted for each NaC1 concentration. o 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. o These cells are said to have increased osmotic fragility and are seen in hereditary spherocvtosis o 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. o These cells with increased surface/volume ratio are osmotically resistant and are seen in iron deficiency, thalassemia, liver disease and reticulocytosis.