Your doctor will diagnose immune thrombocytopenia (ITP) based on your medical history, a physical exam, and test results.
Your doctor will want to make sure that your low platelet count isn't due to another condition (such as an infection) or medicines you're taking (such as chemotherapy medicines or aspirin).
Your doctor may ask about:
- Your signs and symptoms of bleeding and any other signs or symptoms you're having
- Whether you have illnesses that could lower your platelet count or cause bleeding
- Medicines or any over-the-counter supplements or remedies you take that could cause bleeding or lower your platelet count
During a physical exam, your doctor will look for signs of bleeding and infection. For example, your doctor may look for purplish areas on the skin or mucous membranes and pinpoint red spots on the skin. These are signs of bleeding under the skin.
You'll likely have blood tests to check your platelet count. These tests usually include:
- A complete blood count. This test checks the number of red blood cells, white blood cells, and platelets in your blood. In ITP, the red and white blood cell counts are normal, but the platelet count is low.
- A blood smear. For this test, some of your blood is put on a slide. A microscope is used to look at your platelets and other blood cells.
You also may have a blood test to check for the antibodies (proteins) that attack platelets.
If blood tests show that your platelet count is low, your doctor may recommend more tests to confirm a diagnosis of ITP. For example, bone marrow tests can show whether your bone marrow is making enough platelets.
If you're at risk for HIV, hepatitis C, or H. pylori, your doctor may screen you for these infections, which might be linked to ITP.
Some people who have mild ITP have few or no signs of bleeding. They may be diagnosed only if a blood test done for another reason shows that they have low platelet counts.