What blood tests will your doctor run?

In TTP the most important tests are platelet count and ADAMTS13 activity levels1-5

People with TTP have fewer platelets

People with TTP have fewer platelets in their blood than they should1

People with TTP usually have a very low number of platelets in their blood. Your doctor will check whether there are fewer platelets in your blood than there should be.

Number of platelets in 1 liter of blood2,3




During an episode of TTP:



People with TTP have lower ADAMTS13 activity than they should1,3-5

ADAMTS13 helps the blood flow and clot normally. In people with TTP, the ADAMTS13 protein does not work as well as it should, which can lead to dangerous clots. A blood test can tell the doctor how well your ADAMTS13 proteins are working.

ADAMTS13 activity3,6



During an episode of TTP:


Your doctor may also check your blood for organ function1,4

When clots block blood vessels, it can lead to damage in organs like the brain, heart, gastrointestinal tract, and kidneys. Blood tests can tell if there is damage to organs.


Check your blood for organ function


Gastrointestinal tract


  1. Joly BS, Coppo P, Veyradier A. Thrombotic thrombocytopenic purpura. Blood. 2017;129(21):2836-2846. doi:10.1182/blood-2016-10-709857
  2. Farinade A. Lab values, normal adult. Medscape website. May 14, 2019. Accessed December 3, 2021. https://emedicine.medscape.com/article/2172316
  3. Zheng XL, Vesely SK, Cataland SR, et al. ISTH guidelines for the diagnosis of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2020;18(10):2486-2495. doi:10.1111/jth.15006 https://practical-haemostasis.com/Miscellaneous/adamts13_assays.html
  4. Scully M, Hunt BJ, Benjamin S, et al; British Committee for Standards in Haematology. Guidelines on the diagnosis and management of thrombotic thrombocytopenic purpura and other thrombotic microangiopathies. Br J Haematol. 2012;158(3):323-335. doi:10.1111/j.1365-2141.2012.09167
  5. Supplement to (Acquired TTP): George JN. The remarkable diversity of thrombotic thrombocytopenic purpura: a perspective. Blood Adv. 2018;2(12):1510-1516. doi:10.1182/bloodadvances.2018018432
  6. ADAMTS13 assays. Practical-Haemostasis website. Updated October 27, 2021. Accessed December 3, 2021. https://practical-haemostasis.com/Miscellaneous/adamts13_assays.html