Osmotic fragility

How to prepare for the test:

Adult:
No special preparation is necessary for this test.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

This test is performed to detect hereditary spherocytosis and thalassemia.

Hereditary spherocytosis is a relatively common disorder characterized by red blood cells which are intrinsically defective because of their sphere-like shape. These cells have increased osmotic fragility.

Red blood cells from people with thalassemia show some cells with increased osmotic fragility, but a larger fraction with decreased fragility.