2B or not 2B? Disparate discrimination of functional VWF discordance using different assay panels or methodologies may lead to success or failure in the early identification of type 2B VWD

Emmanuel J. Favaloro; Roslyn Bonar; Muriel Meiring; Alison Street; Katherine Marsden; the RCPA QAP in Haematology; on behalf of

doi:10.1160/TH06-12-0693

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2007; 98(02): 346-358
DOI: 10.1160/TH06-12-0693

Blood Coagulation, Fibrinolysis and Cellular Haemostasis

Schattauer GmbH

2B or not 2B? Disparate discrimination of functional VWF discordance using different assay panels or methodologies may lead to success or failure in the early identification of type 2B VWD

Authors

Emmanuel J. Favaloro

¹Departments of Haematology and RCPA Quality Assurance Program (QAP), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, New South Wales, Australia
Roslyn Bonar

¹Departments of Haematology and RCPA Quality Assurance Program (QAP), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, New South Wales, Australia
Muriel Meiring

²Department of Haematology and Cell Biology, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa
Alison Street

¹Departments of Haematology and RCPA Quality Assurance Program (QAP), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, New South Wales, Australia
Katherine Marsden

¹Departments of Haematology and RCPA Quality Assurance Program (QAP), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, New South Wales, Australia

the RCPA QAP in Haematology

Abstract

Summary

Laboratory proficiency in the identification of functional von Willebrand factor (VWF) discordance in type 2B von Willebrand disease (VWD) was assessed by external quality assurance surveys conducted by the RCPA Haematology QAP, and using six different type 2B VWD plasma samples (three historical and three previously unpublished) tested by up to 52 laboratories. For the three most recent samples, functional VWF discordance was either not identified in testing or by interpretation with misidentification as ‘normal’ or ‘type 1 VWD’, on average for 25.7% of test occasions when laboratories performed VWF:Ag and VWF:RCo as their primary VWF test panel, but somewhat fewer occasions (10.9%) for laboratories that incorporated VWF:CB as an additional functional VWF assay. VWF assay sub-methodologies also influenced the appropriate identification of samples as potentially type 2 VWD, and VWF functional discordance was more consistently identified when laboratories used (i) automated platelet agglutination for VWF:RCo compared to classical platelet aggregometry, (ii) inhouse VWF:CB assays compared to commercial kit methods, and (iii) automated LIA-based ‘VWF:Activity’ assays compared to ELISA based assays.We conclude that:(i) laboratories are generally proficient in tests for VWD but interpretative diagnostic errors do occur; (ii) correct diagnosis is more likely when test panels are more comprehensive and include the VWF:CB; (iii) sub-methodology influences the appropriate identification of VWF functional discordance. On the basis of these findings, we provide a series of recommendations to enable the appropriate laboratory identification of VWD, in particular type 2B VWD.

Keywords

von Willebrand factor - VWF - von Willebrand’s disorder - von Willebrand’s disease - VWD - laboratory assessment - survey - haemostasis testing - diagnostic practice - quality control - quality assurance

Full Text

References

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