Evaluation of a rapid von Willebrand Factor Activity Latex Immuno Assay for monitoring of patients with von Willebrand disease (VWD) receiving DDAVP® or VWF replacement therapy

Summary Haemostatic management of surgery in patients with von Willebrand disease (VWD) includes DDAVP® or von Willebrand factor (VWF)‐containing concentrates. Although the recommendations are for monitoring by VWF activity assays, it is quite common for clinicians to use factor VIII due usually to longer turnaround times required for VWF ristocetin cofactor assay (VWF:RCo) measurements. The aim of this study was to evaluate use of the rapid HaemosIL™ VWF activity (VWF:Act) latex immuno assay (LIA) on an automated coagulometer (ACL TOP™ 700; Instrumentation Laboratory, Bedford, MA, USA) compared to platelet‐based VWF:RCo assays in this setting. One hundred and sixty‐seven plasma samples from 42 patients [Type 1 (n = 22), Type 2A (n = 2), Type 2B (n = 3), Type 2M (n = 10), Type 3 (n = 3)] and acquired von Willebrand syndrome (n = 2) with VWD treated with DDAVP® or VWF‐containing concentrates were included in the study. Method comparison and method bias were evaluated by Bland–Altman analysis (BA) and Passing and Bablok regression modelling respectively. BA of baseline samples (n = 39) showed a mean difference of −3.0 (±1.96 SD −25.2 to +19.4). Post (treatment) samples (n = 120) were separated into two groups. Group 1 contained samples with VWF:RCo levels 10 to ≤175 IU dL−1 (n = 97) and group 2, samples with VWF:RCo levels >175 IU dL−1 (n = 23). BA of group 1 postsamples showed a mean difference of +3.4 (±1.96 SD −44.6 to +51.5), and the BA of Group 2 samples was −23.9 (±1.96 SD −136.1 to +88.3). In conclusion, use of HaemosIL VWF:Act LIA test on an automated coagulometer is a reproducible and rapid assay that can be used as an alternative test for monitoring VWF replacement therapy, facilitating dose adjustments on a real‐time basis.