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A two-centre comparative evaluation of new automated assays for von Willebrand factor ristocetin cofactor activity and antigen

Authors

  • F. Stufano,

    Corresponding author
    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
    • Correspondence: Francesca Stufano, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.

      Tel: +39 02-5510709-55035414; fax: +39 02-54100125;

      e-mail: francy.stu@tiscali.it

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  • A. S. Lawrie,

    1. Haemostasis Research Unit, Department of Haematology, University College London, London, UK
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  • S. La Marca,

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
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  • C. Berbenni,

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
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  • L. Baronciani,

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
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  • F. Peyvandi

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
    2. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Università degli Studi di Milano, Milan, Italy
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Summary

von Willebrand disease (VWD) is caused by a quantitative and/or qualitative deficiency of the von Willebrand factor (VWF). The laboratory diagnosis of VWD is dependent on the measurement of VWF antigen (VWF:Ag) and ristocetin cofactor activity (VWF:RCo). The aim of this study was to undertake a two-centre evaluation of two new automated VWF:Ag and VWF:RCo assays systems from Instrumentation Laboratory (Bedford, USA). Using the two new analytical systems that operated with different detection principles: immunoturbidimetric (TOP500 analyser) and chemiluminescent (AcuStar analyser), VWF:Ag and VWF:RCo levels were determined in samples from 171 healthy normal subjects, 80 VWD patients (16 type 1, 58 type 2 and 6 type 3) and 7 acquired von Willebrand syndrome patients. With commercial lyophilized normal and pathological plasmas VWF: Ag and VWF:RCo assays performed on both analysers exhibited low levels of inter-assay imprecision (AcuStar: CV% range 3.3–6.9; TOP500: CV% range 2.6–6.3). Samples from normal healthy subjects (range: VWF:Ag 44.6–173.9 IU dL−1; VWF:RCo 43.1–191.5 IU dL−1) and patients (range: VWF:Ag <0.3–115.1 IU dL−1; VWF:RCo <0.5–57.2 IU dL−1) showed a good correlation between the two VWF:Ag and VWF:RCo methods (rs = 0.92 and 0.82 respectively), with only a few inconsistent cases among the patients' samples evaluated. The chemiluminescent assays had a lower limit of detection for both VWF:Ag and VWF:RCo compared to immunoturbidimetric tests (0.3 IU dL−1 vs. 2.2 IU dL−1 and 0.5 IU dL−1 vs. 4.4 IU dL−1 respectively). The TOP500 and AcuStar VWF:Ag and VWF:RCo assays were precise and compare well between centres, making these systems suitable for the diagnosis of VWD in non-specialized and reference laboratories.

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