HEMA OSMOTIC FRAGILITY TEST Flashcards
Red blood cells are surrounded by a
selectively permeable membrane that
allows the exchange of ___ and ___.
Osmotic Fragility Test
- gases
- electrolytes.
If the RBCs are placed in a ____, osmotic equilibrium will be established by drawing water into the cells, which then swell.
Pathologically,___ of the RBC membrane leads to the accumulation of water within the cell, and finally the escape of _____ through the widened pores of the cell membrane
Osmotic Fragility Test
- hypotonic saline solution
- increased permeability
- hemoglobin
Used for definitive diagnosis or traditional screening test of ____
in combination with other tests such as
blood indices.
Test that demonstrates ______
>RBCs that have decreased surface
area-to-volume ratio (such as ___)
Osmotic Fragility Test
- hereditary spherocytosis
- increased RBC fragility
- spherocytes
Causes of Decreased Surface Area-to-volume ratio
Hereditary spherocytosis
Warm autoimmune hemolytic anemia
Caused by lack of vertical interaction
of the RBC membrane as a result of
_____
Hereditary spherocytosis
spectrin deficiency
RBCs are sensitized by antibodies
known as IgGs that are pitted in the
spleen resulting in ____
formation
Warm autoimmune hemolytic anemia
spherocyte
OFT lacks ____ and ____ because it cannot differentiate whether the cause of spherocyte formation is due to HS or WAIHA
specificity and sensitivity
OFT Principle
Whole blood is added to varying
concentrations of _____, that being buffered ____ and allowed to incubate at room temperature.
hypotonic solution
sodium chloride solution
Precautions in performing OFT
- Blood sample should be obtained with
minimum stasis and trauma. - The test should be set up as soon as
possible. - The sizes of the drops of blood must be
uniform. - Blood should fall directly into the saline
solution and not on the sides of the tubes.
Rejection criteria of OFT
hemolyzed specimen
- Prepare _____
- Arrange _____ and label the tubes from _____
- To each tube, add _____
- The number of drops should correspond to the _____
- Add ____ to each tube. The number of drops should bring the total volume in each tube to __. Mix.
- Deliver a drop of ____ into each tube. Mix gently
- Allow the tubes to stand for __ at ____.
- Examine the tube for initial and complete hemolysis.
Griffin-Sandford Method
0.5% NaCl solution (0.5g NaCl dissolved
100 mL d.H2O).
12 Wassermann tubes
25 down to 14(left to right)
drop by drop 0.5% NaCl
number labeled on each tube
distilled water
25
freshly drawn blood
2 hours
Room temp
Griffin-Sandford Method
Computation: _____
Normal value:
Initial hemolysis - _____
Complete hemolysis _____
Tube number x 0.02 = %
0.44 +/- 0.02% (0.42-0.44%)
0.32 +/-0.02% (0.32-0.34%)
Hemolysis are partial if the fluid(supernatant) turns faintly pink
Sediment or red cells or cell button still present
starts at test tube ___ and ___ in normal biconcave RBC
Initial Hemolysis
22
21
Complete when the fluid (supermatant) is red with no sediments
Sediments or red cell button is not present
Starts at test tube __,___ in normal biconcave RBC
Complete hemolysis
16
17
no hemolysis yet in test tube ___,____,___
25,24,23
Erythrocyte Osmotic Fragility Curve
B
C
A
Normal biconcave RBC
B
Increased OFT/ Shift to the left
___ and ___
C
Spherocytosis
Older red cells
Decreased OFT/ Shift to the right
A
Thalassemia and hemoglobinopathies
Target cells
Younger red cells - reticulocytes
Factors that affect OFT
- Shape of red cells
- Functional state of cell membrane
- Surface-to-volume area
- Chemical purity of sodium chloride
- Accuracy of sodium chloride solution
- Tonicity of solution
- pH must be 7.4 - a change of pH by 0.1 is equal to the change of tonicity by
0.01% - A temperature rise will increase fragility - 5 degrees Celsius change is equal to a change of tonicity of about 0.01%
Increased Osmotic Fragility
Decreased Resistance
Hemolytic anemias
Hereditary spherocytosis,
Whenever spherocytes are found
Decreased Osmotic Fragility
Increased Resistance
Splenectomy
In liver disease,
Sickle cell anemia,
Iron-deficiency anemia,
Thalassemia and
Polycythemia Vera,
Conditions in which target cells are present
Hypertonic
shrink/ crenate
Hypotonic
swell/ lysis -> Hemolysis
