What is the role of von Willebrand factor–cleaving protease (ADAMTS13) measurement in the workup of thrombotic thrombocytopenic purpura (TTP)?

Updated: Feb 18, 2019
  • Author: Theodore Wun, MD, FACP; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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Answer

Although not routinely available, measurement of von Willebrand factor–cleaving protease (ADAMTS13) activity holds the promise of helping diagnose TTP with greater certainty. Ideally, patients with TTP have either an inherited or an acquired lack of this protease activity, whereas those with HUS do not have an abnormality of the enzyme.

To date, however, studies with different variations of the activity assay have not clearly distinguished between patients thought to have TTP from patients thought to have HUS. In addition, patients with other causes of thrombocytopenia—as well as liver disease, pregnancy, and sepsis—may have moderately depressed levels of ADAMTS13 activity. Thus, the diagnostic utility of the assays has yet to be demonstrated.

Wu et al reported that ADAMTS13 response to early plasma exchange therapy in patients with acquired TTP has prognostic value. In their study of 19 patients, recovery of ADAMTS13 activity to more than 10% within 7 days was significantly associated with a timely clinical response. In contrast, patients whose ADAMTS13 level failed to exceed 10% by 7 days tended to experience TTP exacerbation, treatment refractoriness, or death. [13]


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