Abstract Number: PB0626
Meeting: ISTH 2020 Congress
Background: Measurement of von Willebrand factor (VWF) activity levels following treatment with Desmopressin (DDAVP) or VWF containing concentrates in patients with VWD is recommended by various national and international guidelines. UKHCDO recommends during major surgery that factor VIII (FVIII:C) and VWF:RCo levels are used. Therefore, quick turnaround times of test results are essential.
Aims: Investigate a chemiluminescent VWF activity assay (VWF:GP1bR) against our current lyophilised platelet ristocetin based assay (VWF:RCo).
Methods: Residual post treatment samples ( n=53, DDAVP n =6, Haemate P n= 26, Voncento = 1 Alphanate n= 3, Wilate n=3, Wilfactin n= 14) from 24 patients with VWD (types – 1 n=10, 2A n=15, 2B n=6, 2M n= 17, 3 n=2, acquired VWD n =1) were tested using chemiluminescent ACL AcuStar VWF Ristocetin Cofactor activity assay (HemoSIl, USA) (VWF:GP1b:R). VWF:RCo was measured by a lyophilised platelet method with ristocetin (BC von Willebrand assay, Siemens, Germany) on a CS2100i (Sysmex, UK). Both assays were calibrated with standards traceable to the WHO international standard for VWF in plasma.
Results: Bland Altman (BA) analysis of all results calculated a bias of -29.9 (SD = 31.7) with 95% limits of agreement (LoA) -91.9 – 32.2. Additional BA analysis was done by separating the VWF:RCo results into group 1 (VWF:RCo levels < 100 IU/dL) and group 2 (VWF:RCo levels ≥100 IU/dL). Group 1 samples bias was -23.34 (SD =15.53) and 95% LoA -53.78 to 7.1 and group 2, bias was -34.6, (SD = 42.01) with 95% LoA -116.9 to 47.73. FVIII:C levels in 42 (79%) of samples were ≥100 IU/dL. Overall percent difference between results showed that the VWF:GP1bR assay was 31.9% higher with an SD of ±33%.
Conclusions: This study of post infusion monitoring samples showed that VWF:GP1bR levels were generally higher compared to VWF:RCo results. Further investigation is required to evaluate the differences.
To cite this abstract in AMA style:Riddell A, Lanning L, Vinayagam S, Yee TT, Chowdary P. An Evaluation of Treatment Monitoring in Patients with VWD Using a Chemiluminescent (VWF:GP1bR) Assay Compared to a Lyophilised Platelet Assay with Ristocetin (VWF:RCo) [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/an-evaluation-of-treatment-monitoring-in-patients-with-vwd-using-a-chemiluminescent-vwfgp1br-assay-compared-to-a-lyophilised-platelet-assay-with-ristocetin-vwfrco/. Accessed November 26, 2020.
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