title: Increased von Willebrand factor levels in patients with systemic lupus erythematosus reflect inflammation rather than increased propensity for platelet activation.
abstract: BACKGROUND
  von Willebrand factor (VWF) is involved in platelet plug formation and protein transport. Increased VWF levels in systemic lupus erythematous (SLE) are considered risk factors for vascular events. VWF protein levels, however, do not accurately reflect its platelet-aggregating function, which has not been examined in SLE.
  
  
  METHODS
  Cross-sectional study with clinical and laboratory data obtained in patients with SLE (n=92) from a regional lupus registry. VWF function was determined by ristocetin-induced platelet aggregation (VWF ristocetin cofactor, VWF:RCo) and VWF levels by turbidimetric assay (VWF antigen, VWF:Ag). The platelet-aggregating activity per VWF unit was estimated by the VWF RCo/Ag ratio. Healthy controls served as comparators and associations were evaluated by non-parametric methods.
  
  
  RESULTS
  VWF:Ag (142% vs 107%, p=0.001) and VWF:RCo levels (123% vs 78%, p<0.041) were increased in patients with SLE, but VWF RCo/Ag ratio was similar as in controls (0.83 vs 0.82, p=0.8). VWF:Ag levels were higher in patients experiencing serositis but unrelated to other manifestations, thrombotic disease, Systemic Lupus Erythematous Disease Activity Index 2000 or Systemic Lupus International Collaborative Clinics-Damage Index. VWF:Ag levels correlated significantly with VWF:RCo levels (Rs 0.8, p<0.001), erythrocyte sedimentation rate (ESR) (Rs 0.32, p<0.01), anti-dsDNA Ab (Rs 0.27, p<0.01), total IgG (Rs 0.33 p<0.01), fibrinogen (Rs 0.28, p<0.01) and ceruloplasmin (Rs 0.367, p<0.01) levels. VWF:RCo levels were not related to clinical findings but were correlated with ESR, anti-dsDNA and transferrin levels. No serological associations existed for VWF RCo/Ag ratio (all p>0.2).
  
  
  CONCLUSIONS
  In this SLE cohort, VWF:Ag behaved similarly to acute-phase reactants, but VWF:Ag increases were not matched by increases in functional activity per unit of VWF. Thus, more VWF did not increase the propensity for platelet aggregation in SLE.
authors.affiliation: Rheumatology Department, School of Medicine, The University of Western Australia/Consultant, Sir Charles Gairdner Hospital , Perth, Western Australia , Australia.
authors.forename: Johannes C
authors.identifier: 0000-0002-2833-7997
authors.initials: JC
authors.lastname: Nossent
authors.affiliation: Rheumatology Department, School of Medicine & Pharmacology, The University of Western Australia , Crawley, Western Australia , Australia.
authors.forename: Warren D
authors.initials: WD
authors.lastname: Raymond
authors.affiliation: Department of Clinical Medicine , UiT The Arctic University of Norway/Consultant RNNK , Tromsø , Norway.
authors.forename: Gro Østli
authors.initials: GØ
authors.lastname: Eilertsen
keywords: Atherosclerosis; Autoantibodies; Cardiovascular Disease; Inflammation; Systemic Lupus Erythematosus