title: Plasma von Willebrand factor multimer quantitative analysis by in-gel immunostaining and infrared fluorescent imaging.
abstract: BACKGROUND
  Electrophoretic analysis of plasma von Willebrand factor (VWF) multimer distribution and infrastructure is essential for subtyping von Willebrand disease. To improve the sensitivity, precision and efficiency of this assay, we developed and validated a new in-gel infrared fluorescent VWF multimer imaging method to visualize and quantify VWF multimers directly in the agarose gel, thus eliminating electroblotting or autoradiographic steps.
  
  
  METHODS
  VWF multimer analyses of plasma samples from 34 patients with known von Willebrand disease or acquired von Willebrand syndrome, 9 patients with acquired VWF abnormalities, 26 normal volunteer donors and 49 patient samples referred for von Willebrand factor multimer analysis were performed by both traditional autoradiographic and the new infra-red imaging methods and compared. VWF multimer image data were electronically acquired, archived and analyzed.
  
  
  RESULTS
  The in-gel infrared method has a sensitivity of detecting VWF antigen as low as approximately 1.6 IU/dL, a reliable fluorescent intensity with intra- and inter-day variability (CV) of 5% and 6% respectively, and provides superior imaging resolution and shortened test turnaround time. Using intermediate resolution agarose gel electrophoresis, the infra-red method sensitively detects subtle loss of highest molecular weight von Willebrand factor multimers in plasmas with acquired VWF abnormalities and in commercial normal reference plasmas, and provides evidence of increased proteolysis of ultralarge multimers in some type 2 VWD plasmas.
  
  
  CONCLUSIONS
  The in-gel infrared fluorescent VWF multimer imaging method provides a sensitive, reliable, efficient and robust system to improve laboratory testing for von Willebrand disease classification.
authors.affiliation: Special Coagulation Laboratory, Division of Hematopathology, Department of Laboratory Medicine and Pathology, Mayo Clinic Rochester, MN 55905, USA. pruthi.rajiv@mayo.edu
authors.forename: Rajiv K
authors.initials: RK
authors.lastname: Pruthi
authors.forename: Todd M
authors.initials: TM
authors.lastname: Daniels
authors.forename: John A
authors.initials: JA
authors.lastname: Heit
authors.forename: Dong
authors.initials: D
authors.lastname: Chen
authors.forename: Whyte G
authors.initials: WG
authors.lastname: Owen
authors.forename: William L
authors.initials: WL
authors.lastname: Nichols
mesh_terms: D001345:Autoradiography; D004587:Electrophoresis, Agar Gel / Q000379:methods*; D006801:Humans; D014842:von Willebrand Diseases / Q000097:blood; D014841:von Willebrand Factor / Q000032:analysis* / Q000592:standards
chemical_list: D014841:von Willebrand Factor