What is osmotic fragility curve?
After splenectomy the red cells are more homogeneous, the osmotic fragility curve indicating a more continuous spectrum of cells, from fragile to normal. Decreased osmotic fragility indicates the presence of unusually flattened red cells (leptocytes) in which the volume-to-surface area ratio is decreased.
What is the principle of the osmotic fragility test?
The osmotic fragility test (OFT) is used to measure erythrocyte resistance to hemolysis while being exposed to varying levels of dilution of a saline solution. When erythrocytes are exposed to a hypotonic environment, water enters the cell and causes swelling and eventual lysis.
What is the normal osmotic fragility?
With the technique of Parpart et al (1947), the normal range for osmotic fragility of red blood cells had been estimated to include 5%–45% haemolysis at a salt concentration corresponding to 4.5 g NaCl/l (Dacie 1954).
What causes osmotic fragility?
What Is An Osmotic Fragility Test? Two conditions that can cause this to happen are called thalassemia and hereditary spherocytosis (HS). These conditions cause the red blood cells to be more likely to break and become a smaller size. Both thalassemia and HS may lead to hemolytic anemia.
What does increased osmotic fragility mean?
Spherocytic red blood cells have a decreased capacity to expand, and will rupture in mildly hypotonic conditions that fail to lyse normal red cells. They thus exhibit increased osmotic fragility. Osmotic fragility is determined by measuring the degree of hemolysis in hypotonic saline solution.
What is osmotic fragility test enumerate the factors that affect the test?
The extrinsic factors include the type, ionic strength and pH of incubation media, type of anticoagulant and storage time of the blood, ambient temperature, drugs, medicinal plant extracts, xenobiotics, chemical agents; whereas intrinsic factors are age, sex, breed, species, pregnancy, lactation and genetic factors.
Why is osmotic fragility curve S shaped?
The ability of the normal RBC to withstand hypotonicity results from its biconcave shape, which allows the cell to increase its volume by ∼70% before the surface membrane is stretched.
What does decreased osmotic fragility mean?
Osmotic fragility is considered to be decreased if hemolysis is not complete in a 0.30% NaCl solution. Decreased osmotic fragility is associated with chronic liver disease, iron deficiency anemia, thalassemia, hyponatremia (Na < 130 meq/L), polycythemia vera, and sickle cell anemia after splenectomy.
What does high osmotic fragility mean?
Sources of Errors in Hematology and Coagulation The osmotic fragility test is useful for diagnosis of hereditary spherocytic hemolytic anemia. Spherocytes are osmotically fragile cells that rupture more easily in a hypotonic solution than do normal RBCs.
Why osmotic fragility decreased in sickle cell anemia?
The decreased osmotic fragility of the erythrocytes in sickle cell anemia probably results from the cell damage which accompanies repeated sickle-unsickle cycles and which reaches its maximum in the irreversibly sickled cells.