title: Risk of excessive bleeding associated with marginally low von Willebrand factor and mild platelet dysfunction.
abstract: BACKGROUND
  Bleeding symptoms are so commonly reported that it is not known whether they associate causally or coincidentally with mild but measurable primary hemostatic defects. OBJECTIVES/PATIENTS/METHODS: In order to evaluate if the mild primary hemostatic defects are truly causative of increased bleeding symptoms, we surveyed a population of healthy teenagers for bleeding symptoms. Using a case-control approach, we then estimated the risk of excessive bleeding associated with low von Willebrand factor (defined as VWF below the 5th percentile of a normal reference population), and with mild platelet dysfunction [PD, defined as concurrent reduced platelet aggregation responses to two agonists (adenosine diphosphate and epinephrine)].
  
  
  RESULTS
  Excessive bleeding was present in 63 out of 809 teenagers (7.8%). Among the 49 cases who were tested for VWF, low values by three measures were more commonly present than in 166 controls, specifically, ristocetin cofactor (RCo) activity [20.4% vs. 5.4%, odds ratio (OR) 4.5], collagen binding (14.3% vs. 4.2%, OR 3.8), and antigen level (20.4% vs. 6.0%, OR 4.0). The low RCo values ranged from 35 to 45 U dL(-1) except for a single case with 26 U dL(-1). Of the 47 teenagers with excessive bleeding who underwent platelet aggregation studies, reduced responses were more common than in controls (12.8% vs. 4.4%, OR 3.2). Twenty-nine per cent of cases with excessive bleeding had either low RCo or PD.
  
  
  CONCLUSIONS
  Almost one in three teenagers who report excessive bleeding is likely to have a measurable hemostatic disturbance manifested either by marginally low VWF (by three measures) or by mild PD.
authors.affiliation: Department of Laboratory Hematology and Hemostasis Center and University of Iceland Medical School, Landspitali University Hospital, Reykjavik, Iceland.
authors.forename: B R
authors.initials: BR
authors.lastname: Gudmundsdottir
authors.forename: V J
authors.initials: VJ
authors.lastname: Marder
authors.forename: P T
authors.initials: PT
authors.lastname: Onundarson
mesh_terms: D000293:Adolescent; D001791:Blood Platelet Disorders / Q000150:complications*; D016022:Case-Control Studies; D005260:Female; D006470:Hemorrhage / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D008297:Male; D010974:Platelet Aggregation; D010979:Platelet Function Tests; D012306:Risk; D011795:Surveys and Questionnaires; D014841:von Willebrand Factor / Q000032:analysis*
chemical_list: D014841:von Willebrand Factor