Semin Thromb Hemost 2006; 32(5): 492-498
DOI: 10.1055/s-2006-947863
Copyright © 2006 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA.

Laboratory Tests for Measurement of von Willebrand Factor Show Poor Agreement among Different Centers: Results from the United Kingdom National External Quality Assessment Scheme for Blood Coagulation

Steve Kitchen1 , Ion Jennings1 , Tim A.L Woods1 , Dianne P. Kitchen1 , Isobel D. Walker1 , Francis E. Preston1
  • 1United Kingdom National External Quality Assessment Scheme (NEQAS) for Blood Coagulation, Sheffield, United Kingdom
Further Information

Publication History

Publication Date:
24 July 2006 (online)

ABSTRACT

In recognition of the importance of von Willebrand factor (vWF) testing in the diagnosis of von Willebrand disease (vWD), the United Kingdom National External Quality Assessment Scheme for Blood Coagulation regularly distributes samples for determination of vWF:antigen (vWF:Ag). Data from 10 separate surveys performed between 2001 and 2005 are reviewed. These include results from ~200 different centers, of which 55% are within the United Kingdom and the remainder are from other countries. During the period of the surveys, the use of immunoelectrophoresis for determination of vWF:Ag practically disappeared and was largely replaced by latex agglutination assays. The coefficient of variation (CV) of results in different centers was ~15 to 20% for most vWF:Ag techniques, with CVs of ~7% for a fluorescence-based assay. Several different techniques were used for determination of vWF ristocetin cofactor activity (vWF:RCo), all of which were associated with poor agreement among centers as indicated by CVs of 40 to 50%. Several centers calculated the ratio of vWF:Ag/vWF:RCo but with variable success. Ratios compatible with either type 1 or type 2 vWD were obtained on samples from subjects with type 1 vWD, as well as on samples from subjects with genetically confirmed type 2 vWD. Overall, our data show that laboratory testing for vWD remains problematic. It remains to be seen whether newer techniques will offer consistently improved precision.

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Steve KitchenPh.D. 

United Kingdom National External Quality Assessment Scheme (NEQAS) for Blood Coagulation, Rutledge Mews

3 Southbourne Road, Sheffield, [postal code] United Kingdom

Email: Steve.Kitchen@sth.nhs.uk