Osmotic Fragility Testing Flashcards
A measure of the ability of the red cells to take up fluid without lysing.
Osmotic Fragility Test
Principle of Osmotic Fragility Testing:
The osmotic fragility test is a measure of the ability of the red cells to take up fluid without lysing. In this test, whole blood is added to varying concentrations of sodium chloride solution and allowed to incubate at room temperature. The rate of hemolysis is then determined through visual inspection of each saline concentration.
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
Small, round, dense red blood cells with no central pallor.
Spherocyte
Purpose of doing the Osmotic Fragility Testing.
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:
Volume
Surface Area
Functional State of RBC Membrane
Materials needed for Osmotic Fragility Testing:
- 12 test tubes
- Test tube rack
- 0.5% NaCl
- Distilled water
- Sahli pipette
- Heparinized blood
- Dropper
What is the color of the tube stopper used for Osmotic Fragility Testing?
Green Stopper
What is the specimen of choice for Osmotic Fragility Testing?
Heparinized Blood
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 14?
14 gtts 0.5% NaCl
11 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 15?
15 gtts 0.5% NaCl
10 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 16?
16 gtts 0.5% NaCl
9 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 17?
17 gtts 0.5% NaCl
8 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 18?
18 gtts 0.5% NaCl
7 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 19?
19 gtts 0.5% NaCl
6 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 20?
20 gtts 0.5% NaCl
5 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 21?
21 gtts 0.5% NaCl
4 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 22?
22 gtts 0.5% NaCl
3 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 23?
23 gtts 0.5% NaCl
2 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 24?
24 gtts 0.5% NaCl
1 gtts Distilled Water
How many drops of 0.5% NaCl and Distilled Water is placed on test tube 25?
25 gtts 0.5% NaCl
0 gtts Distilled Water
Give the Following:
Value of Test Tube 14
0.28%
Give the Following:
Value of Test Tube 15
0.30%
Give the Following:
Value of Test Tube 16
0.32%
Give the Following:
Value of Test Tube 17
0.34%
Give the Following:
Value of Test Tube 18
0.36%
Give the Following:
Value of Test Tube 19
0.38%
Give the Following:
Value of Test Tube 20
0.40%
Give the Following:
Value of Test Tube 21
0.42%
Give the Following:
Value of Test Tube 22
0.44%
Give the Following:
Value of Test Tube 23
0.46%
Give the Following:
Value of Test Tube 24
0.48%
Give the Following:
Value of Test Tube 25
0.50%
How much blood must be in each test tube?
20 ul (0.02 mL)
What is the time and temperature required for incubation in Osmotic Fragility Testing?
Room Temperature
2 Hours
What is the centrifugation time after the incubation is finished?
5 Minutes
What is the appearance of an Initial Hemolysis?
Tinge of pinkness in the supernatant and some cells at the bottom of the tube.
What is the appearance of a Complete Hemolysis?
Clear, red supernatant with no microscopic cells at the bottom of the tube.
Reference Value for an Initial Hemolysis:
0.42% - 0.44% (Test Tube #21 or Test Tube #22)
Reference Value for a Complete Hemolysis:
0.32% - 0.34% (Test Tube #16 or Test Tube #17)
To get the value in percentage, what do we need to do?
We multiply the number of the tube with initial and complete hemolysis by 0.02 (the amount of blood delivered in each test tube)
Decreased OFT is seen in:
Sickle cell Anemia
Iron-deficiency Anemia
Thalassemia
Polycythemia Vera
Conditions where Target Cells are present
Reticulocytes
Increased OFT is seen in:
Hereditary Spherocytosis
Conditions where Spherocytes are present
Older RBCs