For In Vitro Research Use Only. Chromogenic ELISA for the determination of ADAMTS-13 activity in human plasma. ADAMTS-13 is an enzyme that specifically cleaves unusually large von Willebrand Factor multimers, which induce platelet thrombus formation under high shear stress. If the activity of ADAMTS-13 is lowered for some reason, unusually large vWF multimers may accumulate