Diagnosis of Thrombotic Thrombocytopenic Purpura

Publication Date: July 1, 2020
Last Updated: March 14, 2022


In settings with a timely access to plasma ADAMTS13 activity testing and for patients with a high clinical suspicion (≥90% pretest probability) of iTTP (eg, based on clinical assessment or a formal clinical risk assessment method), the panel suggests the following diagnostic strategy. (Low, Conditional (weak))
  • Step 1: Acquire a plasma sample for ADAMTS13 testing (eg, ADAMTS13 activity and inhibitors or anti‐ADAMTS13 IgG) before an initiation of TPE or use of any blood product.
  • Step 2: Start TPE and corticosteroids without waiting for the results of ADAMTS13 testing.
  • Step 3: Consider early administration of caplacizumab before receiving plasma ADAMTS13 activity results.
  • Step 4: When the result of plasma ADAMTS13 activity is available, continue caplacizumab if ADAMTS13 activity is less than 10 IU/dL (or <10% of normal) (a positive result) or stop caplacizumab and consider other diagnoses if ADAMTS13 activity is >20 IU/dL (or >20% of normal) (a negative result).
  • Step 5: For patients with plasma ADAMTS13 activity less than 10 IU/dL (or <10% of normal) (a positive result), also consider adding rituximab as early as possible, as a majority of these adult patients (>95%) have autoantibodies against ADAMTS13.



Diagnosis of Thrombotic Thrombocytopenic Purpura

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