Osmotic fragility test

Osmotic Fragility Test

An osmotic fragility test is a diagnostic procedure used to determine the presence of abnormal red blood cells in the bloodstream. It is used to diagnose various anemia types such as sickle cell anemia, thalassemia, and hemoglobinopathies.

Preparation

The patient’s blood sample is collected in a tube and diluted with saline. The diluted sample is then placed in a cuvette for testing.

Procedure

The cuvette is placed in a stirring chamber and several different concentrations of a salt solution such as NaCl, KCl, or MgCl2 are added. The salt concentrations are gradually increased, causing the red blood cells to swell. As the salt concentration increases, the red blood cells start to burst due to the osmotic pressure.

Types

• Hyperosmotic Fragility Test - The sample is placed in a solution that is hyperosmotic compared to the red blood cell interior and causes them to increase in volume. The cell membranes become weakened due to the increased volume, leading to cell lysis.
• Hypoosmotic Fragility Test - The sample is placed in a hypotonic solution, causing the red blood cells to shrink due to osmosis. This increase in surface area causes cell lysis.

Risks

The osmotic fragility test is generally safe with few known risks. The most common risk associated with this procedure is the potential for cross-contamination if the patient’s blood is not properly collected and handled.

Why Perform the Test?

The osmotic fragility test is used to diagnose various anemia types such as sickle cell anemia, thalassemia, and hemoglobinopathies. It can also be used to differentiate between red blood cells affected by untreated infectious diseases and red blood cells affected by chronic diseases, such as iron deficiency anemia.

When is the Test Performed?

The osmotic fragility test is usually performed when a patient has signs and symptoms of anemia, such as fatigue, pale skin, and irritability. It can also be used to monitor the progression of a chronic anemia or to see if an anemiacos has been successfully treated.