ADAMTS-13 Activity Assay
(available a la carte only)

Thrombotic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura (TTP) is an ultra-rare disease caused by platelet clumping on aggregated unusually large von Willebrand factor (vWF) multimers, leading to microthrombi formation in small blood vessels and potentially culminating in multi-organ failure. In healthy individuals, ADAMTS13, a circulating protease, specifically cleaves large vWF multimers, significantly reducing platelet thrombi formation under high shear stress. Reduced ADAMTS13 activity (<60%) can be found in the acquired form of TTP in association with ADAMTS13 autoantibodies. ADAMTS13 activity is totally absent (<10%) in the inherited form of TTP, which is known as Upshaw-Schülman syndrome.

Atypical hemolytic uremic syndrome
Atypical hemolytic uremic syndrome (aHUS) is another ultra-rare thrombotic microangiopathy. Although ~50% of cases of aHUS are caused by mutations in genes in the alternative complement pathway, about 60% of aHUS patients are estimated to have reduced ADAMTS13 activity (<60% of normal but above 10% of normal) (1). Whether reduced ADAMTS13 activity is an important component of the aHUS phenotype has not been determined. 

Indications for screening
Screening is appropriate for patients with TTP and aHUS.

MORL Screening Methodology
Fluorescence Resonance Energy Transfer (FRET)

Turnaround time
Turnaround time is ~24 hours. 

Sample Required
1 ml frozen citrated plasma (see testing requisition form for specimen handling).

Cost & CPT Codes

The Clinical Diagnostics Service of the Molecular Otolaryngology & Renal Research Laboratories is a CLIA-approved, Joint Commission-accredited diagnostic laboratory.


Feng S, et al.: Partial ADAMTS13 deficiency in atypical hemolytic uremic syndrome. Blood. 2013 Aug 22;122(8):1487-93. Epub 2013 Jul 11.