title: Evaluation of an heterogeneous group of patients with von Willebrand disease using an assay alternative to ristocetin induced platelet agglutination.
abstract: BACKGROUND
  Diagnosis of von Willebrand disease (VWD) type 2 usually relies on the discrepancy between the von Willebrand factor (VWF) ristocetin cofactor activity (VWF:RCo) and VWF antigen (VWF:Ag). Type 2B patients can be discriminated from other qualitative VWD variants by using ristocetin-induced platelet agglutination (RIPA) test. The major limitation of RIPA is the requirement of fresh blood sample.
  
  
  OBJECTIVE
  In this study, we evaluated the VWF gain-of-function mutant GPIb binding (VWF:GPIbM) and VWF:RCo assays to investigate whether the VWF:GPIbM/VWF:RCo ratio was able to identify the type 2B variant among an heterogeneous VWD population, previously characterized following the ISTH-SSC guidelines.
  
  
  METHODS
  Seventy-six VWD patients and 31 healthy subjects were evaluated by using VWF:Ag, VWF:RCo, and VWF:GPIbM assays.
  
  
  RESULTS
  The mean (minimum-maximum values) VWF:GPIbM/VWF:RCo ratio was higher in type 2B patients (2.53, 0.84-6.11) than in healthy controls (1.05, 0.87-1.34), type 1 (0.85, 0.51-1.15), 2A (1.20, 0.36-2.82), and 2M (1.07, 0.91-1.38) (P < 0.0001). Type 2B variants were divided into four groups (A, B, C, and D) according to their different multimeric patterns. The mean value of the VWF:GPIbM/VWF:RCo ratio in the four groups showed an increasing trend from group A (1.08) to D (3.69), proportional to the loss of high molecular weight multimers. Among 32 type 2B patients, previously diagnosed with RIPA, 8 (mainly with a type I New York/Malmö phenotype) were not confirmed using the VWF:GPIbM/VWF:RCo ratio.
  
  
  CONCLUSIONS
  Whenever the RIPA test is not feasible, the VWF:GPIbM/VWF:RCo ratio might help to identify severe type 2B VWD patients.
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Stufano
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Baronciani
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: M T
authors.initials: MT
authors.lastname: Pagliari
authors.affiliation: Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Franchi
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Cozzi
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Garcia-Oya
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Bucciarelli
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Boscarino
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.|Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy.
authors.forename: F
authors.identifier: http://orcid.org/0000-0001-7423-9864
authors.initials: F
authors.lastname: Peyvandi
mesh_terms: D015415:Biomarkers / Q000097:blood; D001792:Blood Platelets / Q000378:metabolism*; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D006801:Humans; D009154:Mutation; D010974:Platelet Aggregation; D010979:Platelet Function Tests; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000235:genetics / Q000378:metabolism; D011237:Predictive Value of Tests; D055503:Protein Multimerization; D012310:Ristocetin / Q000008:administration & dosage*; D012720:Severity of Illness Index; D056728:von Willebrand Disease, Type 2 / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D019038:Platelet Glycoprotein GPIb-IX Complex; C094990:adhesion receptor; D014841:von Willebrand Factor; D012310:Ristocetin
keywords: GPIbalpha protein, human; ristocetin; von Willebrand disease, type 2; von Willebrand diseases; von Willebrand factor