title: Development of an ELISA method for testing VWF ristocetin cofactor activity with improved sensitivity and reliability in the diagnosis of von Willebrand disease.
abstract: OBJECTIVE
  Current methods in assessing von Willebrand factor (VWF) ristocetin cofactor activity for Von Willebrand's disease (VWD) diagnosis include platelet agglutination by aggregometer or macroscopic slide examination, which are both time-consuming with suboptimal interassay and intra-assay variation. The purpose of this study is to establish a sensitive assay to detect VWF:RCo activity and evaluate its performance in VWD diagnosis.
  
  
  METHODS
  We have established a sensitive VWF:RCo-ELISA method using a monoclonal antibody, SZ-151, to immobilize the recombinant fragment of platelet glycoprotein Ib (rfGPIbα). VWF was captured by rfGPIbα in the presence of ristocetin, and then detected by HRP-conjugated rabbit anti-human VWF IgG. We tested the VWF:RCo level by this VWF:RCo-ELISA in 25 patients with different types of VWD and 36 healthy donors, and compared this method to a previously reported ELISA using 2D4 coating antibody.
  
  
  RESULTS
  The sensitivity of VWF:RCo-ELISA was greatly improved with this assay (0.008 IU/dL compared to 0.031 IU/dL by 2D4 antibody). The interassay and intra-assay coefficient variation were 8% and 12%, respectively. The mean values (ranges) of VWF:RCo in patients with type 1, type 2A, type 2B, type 2M, and type 3 of VWD and control group are 31.8 (22.3-56.9), 4.8 (0.6-11.8), 8.6 (1.6-19.7), 3.9 (1.0-6.8), 1.0 (0.5-1.6), and 91.5 (47.3-169.2) IU/dL, respectively. The corresponding ratios (ranges) of VWF:RCo/VWF:Ag are 0.83 (0.70-1.16), 0.27 (0.08-0.58), 0.31 (0.15-0.40), 0.18 (0.14-0.21), 0.52 (0.13-1.19), and 0.92 (0.62-1.26).
  
  
  CONCLUSIONS
  The VWF:RCo-ELISA using monoclonal anti-rfGPIbα antibody SZ-151 showed improved sensitivity and reliability in detecting VWF:RCo activity, and its clinical application would facilitate the diagnosis and classification of VWD.
authors.affiliation: Jiangsu Institute of Hematology, The First Affiliated Hospital of Soochow University, Key Laboratory of Thrombosis and Haemostasis, Ministry of Health, Suzhou 215006, China. zhaoyimingbox@163.com
authors.forename: Yiming
authors.initials: Y
authors.lastname: Zhao
authors.forename: Ying
authors.initials: Y
authors.lastname: Gu
authors.forename: Shundong
authors.initials: S
authors.lastname: Ji
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Yang
authors.forename: Ziqian
authors.initials: Z
authors.lastname: Yu
authors.forename: Changgeng
authors.initials: C
authors.lastname: Ruan
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D012310:Ristocetin / Q000378:metabolism*; D012680:Sensitivity and Specificity; D014842:von Willebrand Diseases / Q000175:diagnosis*
chemical_list: D012310:Ristocetin