Laboratory Testing for von Willebrand’s Disease: An Assessment of Current Diagnostic Practice and Efficacy by Means of a Multi-laboratory Survey

Emmanuel J. Favaloro; Julian Smith; Penny Petinos; Mark Hertzberg; Jerry Koutts; the RCPA Quality Assurance Program (QAP) in Haematology Haemostasis Scientific Advisory Panel; on behalf of

doi:10.1055/s-0037-1614375

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 1999; 82(04): 1276-1282
DOI: 10.1055/s-0037-1614375

Review Article

Schattauer GmbH

Laboratory Testing for von Willebrand’s Disease: An Assessment of Current Diagnostic Practice and Efficacy by Means of a Multi-laboratory Survey

Authors

Emmanuel J. Favaloro

¹From the Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Western Sydney Area Health Service, Westmead, NSW, Australia
Julian Smith

¹From the Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Western Sydney Area Health Service, Westmead, NSW, Australia
Penny Petinos

¹From the Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Western Sydney Area Health Service, Westmead, NSW, Australia
Mark Hertzberg

¹From the Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Western Sydney Area Health Service, Westmead, NSW, Australia
Jerry Koutts

¹From the Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Western Sydney Area Health Service, Westmead, NSW, Australia

Authors

the RCPA Quality Assurance Program (QAP) in Haematology Haemostasis Scientific Advisory Panel

Abstract

Summary

We report an evaluation of current laboratory practice for the diagnosis of von Willebrand’s disease (VWD) by means of a multilaboratory survey. This assessment was undertaken with the RCPA Quality Assurance Program (QAP) in Haematology, which covers a wide geographic area encompassing Australia, New Zealand and Asia. A total of 25 laboratories actively involved in testing for VWD were selected to participate in a sample testing assessment exercise. Samples comprised 10 plasmas: (i) a normal plasma pool (in duplicate), (ii) this pool diluted to 50% (in duplicate), (iii) a normal individual (×1), (iv) severe Type 1 VWD (×1), (v) Type 2B VWD (×2 unrelated donors), (vi) Type 3 VWD (×1), (vii) Type 2A VWD (×1). Laboratories were asked to perform all tests available to them in order to establish a laboratory diagnosis of VWD, and then to comment on the possibility or otherwise of VWD. Overall findings indicated a wide variation in test practice, in the effectiveness of various test procedures in detecting VWD, and in the ability of various composite test panels to identify type 2 VWD subtypes. Firstly, while all laboratories (n = 25) performed tests for FVIII:C activity, von Willebrand factor ‘antigen’ (VWF:Ag) and a functional VWF assay [using the ristocetin cofactor assay (VWF:RCo; n = 23) and/or the collagen binding assay (VWF:CBA; n = 12)], only three laboratories carried out VWF:Multimer analysis. Secondly, for the three quantitative VWF assays, 10/25 (40%) laboratories performed all three, whereas 15/25 (60%) performed only two [VWF:Ag and VWF:RCo (n = 13); VWF:Ag and VWF:CBA (n = 2)]. Thirdly, a variety of assay methodologies were evident for VWF:Ag [ELISA, electro-immuno diffusion (EID), latex immuno-assay (LIA), and VIDAS assay] and VWF:RCo (platelet agglutination/‘aggregometry’ and a ‘functional VWF:RCo-alternative’ ELISA assay). Between method analysis for the quantitative VWF assays showed that the VWF:RCo yielded the greatest degree of inter-laboratory assay variation, and had the poorest overall performance with respect to sensitivity to low levels of VWF. The VWF:CBA also performed better than the VWF:RCo in terms of ability to detect functional VWF ‘discordance’ (i.e. Type 2 VWD). Within VWF:Ag method analysis showed that the EID assay procedure was associated with the greatest variation in assay

Full Text

References

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