OF TEST Flashcards
Principle of OF test
The osmotic fragility test is a measure of the ability of the red cells to take up fluid without lysing.
– the relative concentration of solutes dissolved in a solution which determine the
direction and extent of diffusion.
Tonicity
solution with the same number of solute particles as the cell
Isotonic
solution with fewer solute particles per liter of solution
Hypotonic –
– solution with higher solute particles per liter of solution
Hypertonic
– red cell with peripheral rim of
hemoglobin surrounded by clear area and central
hemoglobinized area (bull’s eye)
Target cell/Codocyte/Mexican hat cell
Modified true or false:
This test is employed to diagnose conditions in which the physical properties of red blood cells
are altered.
The shape of the red blood cells is the primary factor affecting the osmotic fragility
test, which, in turn, depends on the volume, surface area and functional state of the red blood
cell membrane.
Both is true
Modified true or false:
Increased osmotic fragility is found in hemolytic anemias and hereditary spherocytosis.
Decreased osmotic fragility is seen in sickle cell anemia, iron-deficiency anemia, thalassemia,
polycythemia and conditions where target cells are present.
Both are true
Materials in OF TEST
Materials:
12 test tubes
Test tube rack
0.5% NaCl
Distilled water
Sahli pipette
Heparinized blood
Dropper
Reference value of OF Test
Initial hemolysis: 0.42-0.44% (Test tube #21 or 22)
Complete hemolysis: 0.32-0.34% (Test tube #16 or 17)
Decreased oft related to:
Decreased OFT: sickle cell anemia, iron-deficiency anemia, thalassemia, polycythemia vera,
conditions where target cells are present, reticulocytes
Increased oft related to:
Increased OFT: hereditary spherocytosis, conditions where spherocytes are present, older
RBCs
