How Immune Thrombocytopenia Is Diagnosed

Immune thrombocytopenia (ITP) is a diagnosis made when the immune system destroys platelets inappropriately, resulting in low platelet counts in the blood. It is often considered a diagnosis of exclusion—when other testing to determine the cause of the low platelets has not shown any specific cause. Therefore, it is likely due to the immune system's destruction of platelets. It may also be diagnosed when ITP is suspected and platelets increase with the medications used to treat ITP.

This article covers diagnostic options for ITP.

Self-Checks/At-Home Testing

There are often no symptoms present when someone has ITP. However, it is possible that some symptoms may be present and may include:

• Bruising, possibly with no known cause
• Petechiae (small, pinpoint red spots often occurring in groups on the skin)
• Bleeding from the gums or blood blisters in the mouth
• Nosebleeds that may occur frequently
• Heavy menstrual cycles
• Blood in urine, stool, or vomit
• Fatigue
• Stroke-like symptoms

There is no test that can be run in the home to diagnose ITP.  

Physical Examination

When being evaluated by a medical professional for ITP, exams may include:

• A skin check, looking for any evidence of bleeding, such as bruises or petechiae
• Inspection of the mouth and gums, looking for bleeding or blood blisters
• Examination of the abdomen to feel for the size of the spleen, as sometimes the spleen is enlarged in ITP

Labs and Tests

There are a variety of tests that may be ordered by the healthcare provider when evaluating ITP or its cause. These include:

• Complete blood count (CBC): A CBC is a blood test that measures the number of white blood cells, red blood cells, and platelets in the blood. This test also measures the size of the blood cell types. Thrombocytopenia is diagnosed when the platelet levels are lower than normal. However, a diagnosis of ITP cannot be made until other potential causes of low platelets have been ruled out.
• Blood smear: In a blood smear, a sample of blood is taken and placed on a slide. This slide is then evaluated under the microscope. The platelets can be evaluated for the proper size and appearance. This visualization also ensures there is no platelet clumping. With platelet clumping, the platelets stick to each other, making them appear low in the blood circulation when they are actually normal in number.
• Bone marrow biopsy: This is not a test often done for ITP, but can be useful in some cases. During a bone marrow biopsy, a small amount of bone marrow is removed from inside a bone in the hip area. The bone marrow is then evaluated for any signs of abnormal cell development. If the healthcare provider is concerned about a diagnosis of a more serious illness causing the platelets to be low, such as leukemia, a bone marrow biopsy may be needed.
• Antiplatelet antibodies: It is possible to test for the presence of antibodies made to platelets, which would result in the inappropriate destruction of platelets. However, this test is not often used in clinical practice, as some studies have shown up to 50% of people with ITP did not test positive with this test.
• Other blood tests: Sometimes healthcare providers may order additional blood testing, such as for the presence of inflammatory markers that may indicate an autoimmune disorder might be present, which could contribute to the development of ITP. 

Imaging

Imaging of the abdomen with a computed tomography (CT) scan, magnetic resonance imaging (MRI), or ultrasound can evaluate the abdominal organs of the liver and spleen.

Sometimes dysfunction in these organs can lead to the development of low platelets. If there is any abnormality of the liver or spleen, this likely is causing the low platelets, not ITP.

Differential Diagnosis

A finding of low platelets may be caused by other illnesses or conditions other than ITP, including:

• TTP (thrombotic thrombocytopenic purpura): Low platelets can be found in TTP, but for a different reason than ITP. In TTP, there is not enough activity by a protein called ADAMTS13. This leads to too many clots forming in the blood, and the circulating platelets are low because they are all being used up in these clots.
• Drug-induced thrombocytopenia: Drug-induced thrombocytopenia occurs when a medication destroys platelets or prevents the body from making enough platelets. This can happen with a variety of medications, most commonly a medication called heparin. Other medications with this risk include penicillin, nonsteroidal anti-inflammatory medications, quinine, sulfa medications, and statin medications.
• Myelodysplastic syndrome: In myelodysplastic syndrome, the bone marrow is not functioning properly, and is unable to produce adequate numbers of blood cells. Although platelets may be affected, white blood cells and red blood cells may be too low as well.
• Viral infection: Some viral infections, such as HIV, viral hepatitis, or the Epstein-Barr virus, may cause platelets to be low through the destruction of platelets or preventing the body from making them properly.

Summary

Immune thrombocytopenia (ITP) is a diagnosis made when the immune system destroys platelets inappropriately, resulting in low platelet counts in the blood. There are various methods of diagnosis for ITP.

A Word From Verywell

Be sure to speak to your healthcare team if you are concerned about the development of ITP, or if you are concerned that you may have low platelets. Testing may be done that can help determine the cause of the low platelets as well as a treatment plan. Also be sure to seek medical care emergently if you have ITP or any other platelet disorder and you are experiencing bleeding.