What is the osmotic fragility test?

By William Aird

Measures red blood cell (RBC) lysis incubated in solution of varying concentrations of sodium chloride. RBC lysis is measured by detection of light absorbance by free hemoglobin immediately after sampling and after 24-hour incubation at 37 degrees C (98.6 degrees F). Osmotically fragile cells, such as spherocytes, lyse at relatively lower saline concentrations compared to normal RBCs.