title: Evaluation of von Willebrand factor-cleaving protease activity in patients with thrombotic thrombocytopenic purpura.
abstract: BACKGROUND
  Thrombotic thrombocytopenic purpura (TTP) is a rare thrombotic microangiopathy. In this study we investigated the von Willebrand factor-cleaving protease (vWF-cp) activity deficiency in patients with TTP.
  
  
  METHODS
  The plasma or serum vWF-cp activity was measured using a sensitive enzyme-linked immunosorbent assay (ELISA) by detecting the residual collagen binding activity (R-CBA) of von Willebrand factor (vWF) before and after digestion by vWF-cp. Multimers of vWF in plasma of patients with TTP were also analyzed by SDS-agarose electrophoresis. Moreover, the serum vWF-cp activities were compared between the patients with TTP and those with tumors.
  
  
  RESULTS
  The coefficient of variation for intra-batch and inter-batch of the assay were 3.60% and 8.35%. The plasma and serum vWF-cp activity in healthy individuals were (78.79 +/- 9.17)% (n = 30) and (79.47 +/- 10.78)% (n = 53), respectively, while the plasma vWF-cp activity in 5 patients with TTP was markedly decreased [(21.83 +/- 19.98)%, P < 0.001]. The unusually large vWF multimers were observed in two plasma samples of the patients with TTP. Although the vWF-cp activities in patients with benign and malignant tumors were also decreased (P < 0.03 and P < 0.001, respectively), they were relatively high in comparison with that of TTP patients (P < 0.001).
  
  
  CONCLUSIONS
  Measurement of the vWF-cp activity using R-CBA is a simple and rapid method for diagnosing TTP. The vWF-cp activity in patients with TTP was markedly lower than those of patients with tumors.
authors.affiliation: Thrombosis and Hemostasis Research Unit, Jiangsu Institute of Hematology, First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Wei-qiang
authors.initials: WQ
authors.lastname: Gao
authors.forename: Jian
authors.initials: J
authors.lastname: Su
authors.forename: Xia
authors.initials: X
authors.lastname: Bai
authors.forename: Zhao-yue
authors.initials: ZY
authors.lastname: Wang
authors.forename: Chang-geng
authors.initials: CG
authors.lastname: Ruan
mesh_terms: D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008666:Metalloendopeptidases / Q000097:blood / Q000172:deficiency*; D008875:Middle Aged; D009369:Neoplasms / Q000201:enzymology; D011697:Purpura, Thrombotic Thrombocytopenic / Q000201:enzymology*
chemical_list: D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human