ADAMTS13 Inhibitor Assay

Test Mnemonic


CPT Codes

  • 85335 - QTY (1)
  • 85390 - QTY (1)



Performing Laboratory

Cleveland Clinic Laboratories

Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
2 mLPlasmaSodium citrate (Lt. Blue) Frozen 

Days Performed

Mon - Fri

Turnaround Time

2 - 4 days


Name Description
Fluorescence Immunoassay 

Reference Range

ADAMTS13 Inhibitor
Sex Age From Age To Type Range Range Unit
   Years99 YearsNormal< or = 0.4 Inhib Unit

Clinical Info

ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13) is responsible for regulating the interaction of platelets with von Willebrand factor (VWF) and proteolytic cleavage of VWF multimers at the Tyr(1605)-Met(1606) bond in the A2 domain of VWF. Measurement of ADAMTS13 activity and its inhibitor is crucial in the diagnosis of thrombotic thromboctyopenic purpura (TTP) and further differentiation of congenital (Upshaw-Schulman syndrome) versus acquired (e.g. autoimmune-related disorder) etiology. TTP is a rare life-threatening disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, variable organ damage and severely deficient ADAMTS13 activity. ADAMTS13 activity in TTP will be less than 5-10% in two-thirds of TTP patients and often related to autoantibodies that inhibit or clear ADAMTS13. Inhibitory antibody is observed in 44-93% of patients with severely deficient ADAMTS13 activity. Persistence of severe deficiency of ADAMTS13 activity or an inhibitor suggests high risk of relapse in symptomatic TTP.