An international collaborative study to compare different von Willebrand factor glycoprotein Ib binding activity assays: the COMPASS‐VWF study

摘要

Essentials New VWF activity assays are increasingly used but information on their comparability is limited. This is an ISTH SSC‐organized study (expert labs, 5 countries) to compare all available assays. VWF activity by six assays correlated well with each other. The new assays show improved characteristics ‐ minor differences are noted. Summary Background Several new assays have become available to measure von Willebrand factor ( VWF ) activity. The new assays appear to have improved performance characteristics compared with the old reference standard, ristocetin cofactor activity ( VWF : RC o), but information is limited about how they compare with VWF : RC o and each other. Methods The von Willebrand factor Subcommittee of the International Society for Thrombosis and Haemostasis ( ISTH ) Scientific and Standardization Committee ( SSC ) designed a collaborative study involving expert laboratories from several countries to compare available tests with each other and with VWF : RC o. Eight laboratories from five countries were provided with blinded samples from normal healthy individuals and well‐characterized clinical cases. Laboratories measured VWF activity using all tests available to them; data from six laboratories, not affected by thawing during transportation, are included in this study. Results All tests correlated well with VWF : RC o activity ( r ‐values ranged from 0.963 to 0.989). Slightly steeper regression lines for VWF :Ab and VWF : GPI bM were clinically insignificant. The new assays showed improved performance characteristics. Of the commercially available assays, the VWF : GPI bR using the AcuStar system was the most sensitive and could reliably detect VWF activity below 1? IU ? dL ?1 . The lower limit of the measuring interval for the VWF : GPI bM and the VWF : GPI bR assays was in the 3–4 and 3–6? IU ? dL ?1 range, respectively. Inter‐laboratory variation was also improved for most new assays. Conclusion All VWF activity assays correlated well with each other and the VWF : RC o assay. The slight differences in characteristics found in the COMPASS ‐ VWF study will assist the VWF community in interpreting and comparing activity results.