Mariam Swidan: Some Red Blood Cells Can’t Handle Pressure
Mariam Swidan, Biomedical Science Graduate, Clinical Laboratory Professional, shared a post on LinkedIn:
“Clinical Lab Concepts 10- Osmotic Fragility
Some RBCs can’t handle pressure. We can prove it.
Osmotic fragility measures how susceptible red blood cells are to hemolysis when placed in hypotonic solutions.
Principle
RBCs are added to a series of saline solutions with decreasing concentrations. As the solution becomes more hypotonic, water enters the cells, then RBCs swell and rupture (hemolysis).
Normal RBCs:
- Biconcave shape enhances flexibility
- Swell gradually
- Lyse later
Spherocytes:
- Decreased Surface area-to-volume ratio
- Reduced Membrane flexibility
- Rupture much earlier
Earlier hemolysis causes a leftward shift in the curve.
The concentration at which hemolysis begins and completes reflects membrane integrity.
Clinical Relevance
- Increased osmotic fragility: Hereditary spherocytosis, AIHA
- Decreased fragility: Thalassemia, target cells
Limitations
Should be interpreted alongside peripheral smear and other hemolysis markers.
Takeaway
Osmotic fragility reflects RBC membrane stability and surface area relationships; A key in identifying spherocytic disorders
Same RBCs. Different shapes. Completely different survival.”

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