Last updated March 14, 2022

Diagnosis of Thrombotic Thrombocytopenic Purpura

Recommendations

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.
612

In settings with a timely access to plasma ADAMTS13 testing and for patients with intermediate or low clinical suspicion 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 inhibitor or anti‐ADAMTS13 IgG) before an initiation of TPE or use of any blood product.
  • Step 2: Consider starting TPE and corticosteroids, depending on the clinician's judgment and assessment of the individual patient.
  • Step 3: Do not start caplacizumab until the result of plasma ADAMTS13 activity becomes available.
  • Step 4: When the result of plasma ADAMTS13 activity testing is available, consider adding caplacizumab and rituximab if ADAMTS13 activity is less than 10 IU/dL (or <10% of normal) with inhibitors or an elevated level of anti‐ADAMTS13 IgG (a positive test result), but do not start caplacizumab and consider other diagnoses if ADAMTS13 activity is greater than 20 IU/dL (or >20% of normal) (a negative result).
612

In settings of no reasonable access to plasma ADAMTS13 activity testing, the panel suggests that caplacizumab not be used, regardless of the pretest probability of TTP. (Low, Conditional (weak))
612

Recommendation Grading

Overview

Title

Diagnosis of Thrombotic Thrombocytopenic Purpura

Authoring Organization

Publication Month/Year

July 1, 2020

Document Type

Guideline

External Publication Status

Published

Country of Publication

US

Inclusion Criteria

Female, Male, Adult

Health Care Settings

Ambulatory, Hospital, Long term care

Intended Users

Physician, nurse, nurse practitioner, physician assistant

Scope

Diagnosis, Management

Diseases/Conditions (MeSH)

D003933 - Diagnosis, D011697 - Purpura, Thrombotic Thrombocytopenic

Keywords

diagnosis, thrombosis, Guidelines, TTP, ADAMTS13