The NESTROFT test is based on the principle of osmotic fragility of red blood cells (RBCs). It checks how easily RBCs burst (hemolyze) when placed in a hypotonic saline solution. In this test, a patient’s blood is mixed with a very dilute sodium chloride (NaCl) solution (usually 0.36% saline) in a single test tube. After incubation, the tube is examined by naked eye against a light source