What Is an Osmotic Fragility Test?
fragility test is used to diagnose two hereditary conditions: thalassemia and
your body to make an abnormal form of hemoglobin. Hemoglobin is the protein
that allows red blood cells to carry oxygen. If you have thalassemia, your red
blood cells are more likely to be destroyed. This can lead to anemia.
spherocytosis causes problems with the outer layer of your red blood cells,
distorting their shape. This can also lead to anemia.
osmotic fragility test, you’ll need to give a blood sample. Your red blood
cells will be tested to see how easily they break. If your red blood cells are
more fragile than normal, the test is considered positive.
Why Doctors Order Osmotic Fragility Tests
order osmotic fragility tests for infants with a family history of thalassemia
or hereditary spherocytosis. This is a faster way to diagnose the disease
rather than waiting for genetic tests. It also allows a doctor to identify
patients who show symptoms of disease. Some people will have the genetic
mutation but not show symptoms.
The test may
also be used to diagnose symptoms of anemia, such as:
- shortness of breath
- chronically cold hands and feet
This can help
identify genetic diseases which cause anemia in people who don’t know they’re
How Is the Test Performed?
There are no
special preparations required for the test. It’s a simple blood test, also
known as a venipuncture. It can be performed in either a lab or a doctor’s
wearing a long-sleeved shirt, the technician will ask you to roll up one of
your sleeves or to remove your arm from the sleeve. The technician will tie a
piece of rubber tightly around your upper arm to help the veins stand out. You
may find this part of the process uncomfortable.
technician will find a vein and clean the area with rubbing alcohol. They’ll
insert a hollow needle into the vein. For most people, this sensation feels
like a sharp pinch.
collecting enough blood, the technician will remove the needle. You’ll need to
keep pressure on the puncture for a few seconds. Then, they'll cover the wound
with a bandage.
Risks of the Test
drawn carries few risks. The greatest risk, which occurs extremely rarely, is
infection. Tell your doctor if you start running a temperature above 100
degrees F. You should also seek help if the skin around the puncture becomes
red, swollen, or painful to touch.
For a few
days after the test, the skin around the puncture may be bruised or tender.
This is normal. Applying ice to the area can reduce bruising and ease
discomfort. Unless your doctor tells you otherwise, you’re free to resume all
normal activities after the test.
Understanding Your Results
A doctor will
look at your blood sample under a microscope. They’re looking for red blood
cells that are smaller than normal or have an unusual shape. To test the
fragility of your red blood cells, your doctor will add them into solutions
with different salt concentrations. Normal blood cells can stay intact at lower
salt concentrations than fragile blood cells.
If your cells
are diagnosed as fragile, you probably have either hereditary spherocytosis or
thalassemia. Both of these genetic conditions can cause hemolytic anemia. This
is a form of anemia that occurs because your red blood cells are destroyed too
quickly. If your osmotic fragility test is positive, the next step is to test
whether you are actively anemic.
with these diseases will have the same level of symptoms. Some people will have
only mild forms with occasional symptoms. Others will have severe forms that
require immediate treatment and may shorten the life span.
doctor determines how severe your condition is, you’ll discuss your treatment
needs. If your illness is mild and you have few symptoms, watchful waiting may
be all that’s necessary. Treatment for severe disease will depend on your