ADAMTS13 Inhibitor
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.

Quantitative Enzyme-Linked Immunosorbent Assay
1-3 days
New York DOH Approval Status
Specimens from New York clients will be sent out to a New York DOH approved laboratory, if possible.
Submit With Order
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
Light Blue (Sodium Citrate). Refer to Specimen Handling at 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.) 
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.

Compliance Statement B: For laboratory developed tests not using a RUO kit, and for FDA approved, cleared or 510(k) exempt assays with alterations. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.

Hotline History
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Component Test Code*Component Chart NameLOINC
3000229ADAMTS13 Inhibitor40824-5
* 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.
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