Ordering Recommendation

Assist in distinguishing between inherited and acquired forms of thrombotic thrombocytopenic purpura (TTP).  Recommended initial test for the identification of autoantibodies to ADAMTS13, since the ADAMS13 inhibitor test is more specific for acquired TTP than the ADAMTS13 antibody test.  If suspicion for TTP remains after a negative result, ADAMTS13 Antibody (3000182) is recommended.

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Light Blue (Sodium Citrate). Refer to Specimen Handling at aruplab.com for hemostasis/thrombosis specimen handling guidelines.

Specimen Preparation

Transfer 1 mL platelet-poor plasma to an ARUP Standard Transport Tube. (Min: 1 mL)

Storage/Transport Temperature

CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Unacceptable Conditions

Serum or EDTA plasma. Clotted or hemolyzed specimens.


Ambient: 2 hours; Refrigerated: Unacceptable; Frozen: 2 weeks (No freeze/thaw cycles.)


Quantitative Enzyme-Linked Immunosorbent Assay




1-3 days

Reference Interval

0.4 BU (Bethesda Units) or less

Interpretive Data

The majority of cases of idiopathic thrombotic thrombocytopenic purpura (TTP) are caused by ADAMTS13 autoantibodies. Autoantibodies that neutralize ADAMTS13 function are found in approximately two-thirds of idiopathic cases and can be identified and titered by the ADAMTS13 inhibitor test. Non-neutralizing autoantibodies that result in increased ADAMTS13 clearance, but do not inhibit function, are found in approximately one-third of idiopathic TTP cases. Non-neutralizing antibodies are not detected in the inhibitor test but can be detected by ELISA (ADAMTS13 antibody test). ADAMTS13 autoantibodies are not present in congenital TTP (Upshaw-Schulman syndrome). Correlation with clinical information, ADAMTS13 activity, and other relevant laboratory testing is suggested.

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.

Compliance Category

Laboratory Developed Test (LDT)


Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
3000229 ADAMTS13 Inhibitor 40824-5
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • von Willebrand Factor Cleaving Protease Inhibitor
ADAMTS13 Inhibitor