Your doctor will diagnosis thrombotic thrombocytopenic purpura (TTP) based on your medical history, a physical exam, and test results.
                
If TTP is suspected or diagnosed, a hematologist will be involved in your care. A hematologist is a doctor who specializes in diagnosing and treating blood disorders.
                
Medical History
                
Your doctor will ask about factors that may affect TTP. For example, he or she may ask whether you:
                
Have certain diseases or conditions, such as cancer, HIV, lupus, or infections (or whether you're pregnant).
                
Have had previous medical procedures, such as a blood and marrow stem cell transplant.
                
Take certain medicines, such as ticlopidine, clopidogrel, cyclosporine A, or hormone therapy and estrogens, or whether you've had chemotherapy.
                
Have used any products that contain quinine. Quinine is a substance often found in tonic water and nutritional health products.
                
Physical Exam
                
As part of the medical history and physical exam, your doctor will ask about any signs or symptoms you've had. He or she will look for signs such as:
                
Bruising and bleeding under your skin
                
Fever
                
Paleness or jaundice (a yellowish color of the skin or whites of the eyes)
                
A fast heart rate
                
Speech changes or changes in awareness that can range from confusion to passing out
                
Changes in urine
                
Diagnostic Tests
                
Your doctor also may recommend tests to help find out whether you have TTP.
                
Complete Blood Count
                
This test measures the number of red blood cells, white blood cells, and platelets in your blood. For this test, a sample of blood is drawn from a vein, usually in your arm.
                
If you have TTP, you'll have a lower than normal number of platelets and red blood cells (anemia).
                
Blood Smear
                
For this test, a sample of blood is drawn from a vein, usually in your arm. Some of your blood is put on a glass slide. A microscope is then used to look at your red blood cells. In TTP, the red blood cells are torn and broken.
                
Platelet Count
                
This test counts the number of platelets in a blood smear. People who have TTP have a lower than normal number of platelets in their blood. This test is used with the blood smear to help diagnose TTP.
                
Bilirubin Test
                
When red blood cells die, they release a protein called hemoglobin (HEE-muh-glow-bin) into the bloodstream. The body breaks down hemoglobin into a compound called bilirubin. High levels of bilirubin in the bloodstream cause jaundice.
                
For this blood test, a sample of blood is drawn from a vein, usually in your arm. The level of bilirubin in the sample is checked. If you have TTP, your bilirubin level may be high because your body is breaking down red blood cells faster than normal.
                
Kidney Function Tests and Urine Tests
                
These tests show whether your kidneys are working well. If you have TTP, your urine may contain protein or blood cells. Also, your blood creatinine (kre-AT-ih-neen) level may be high. Creatinine is a blood product that's normally removed by the kidneys.
                
Coombs Test
                
This blood test is used to find out whether TTP is the cause of hemolytic anemia. For this test, a sample of blood is drawn from a vein, usually in your arm.
                
In TTP, hemolytic anemia occurs because red blood cells are broken into pieces as they try to squeeze around blood clots.
                
When TTP is the cause of hemolytic anemia, the Coombs test is negative. The test is positive if antibodies (proteins) are destroying your red blood cells.
                
Lactate Dehydrogenase Test
                
This blood test measures a protein called lactate dehydrogenase (LDH). For this test, a sample of blood is drawn from a vein, usually in your arm.
                
Hemolytic anemia causes red blood cells to break down and release LDH into the blood. LDH also is released from tissues that are injured by blood clots as a result of TTP.
                
ADAMTS13 Assay
                
A lack of activity in the ADAMTS13 enzyme causes TTP. For this test, a sample of blood is drawn from a vein, usually in your arm. The blood is sent to a special lab to test for the enzyme's activity.