Von Willebrand factor collagen-binding capacity predicts in-hospital mortality in COVID-19 patients: insight from VWF/ADAMTS13 ratio imbalance.

Microthrombosis is a hallmark of COVID-19. We previously described von willebrand factor (VWF) and their high molecular weight multimers (HMWMs) as potential trigger of microthrombosis. Investigate VWF activity with collagen-binding assay and ADAMTS13 in COVID-19. Our study enrolled 77 hospitalized COVID-19 patients including 37 suffering from a non-critical form and 40 with critical form. Plasma levels of VWF collagen-binding ability (VWF:CB) and ADAMTS13 activity (ADAMTS13:Act) were measured in the first 48 hours following admission. VWF:CB was increased in critical (631% IQR [460–704]) patients compared to non-critical patients (259% [235–330], p < 0.005). VWF:CB was significantly associated (r = 0.564, p < 0.001) with HMWMs. Moreover, median ADAMTS13:Act was lower in critical (64.8 IU/dL IQR 50.0–77.7) than non-critical patients (85.0 IU/dL IQR 75.8–94.7, p < 0.001), even if no patients displayed majors deficits. VWF:Ag-to-ADAMTS13:Act ratio was highly associated with VWF:CB (r = 0.916, p < 0.001). Moreover, VWF:CB level was highly predictive of COVID-19 in-hospital mortality as shown by the ROC curve analysis (AUC = 0.92, p < 0.0001) in which we identified a VWF:CB cut-off of 446% as providing the best predictor sensitivity–specificity balance. We confirmed this cut-off thanks to a Kaplan–Meier estimator analysis (log-rank p < 0.001) and a Cox-proportional Hazard model (HR = 49.1, 95% CI 1.81–1328.2, p = 0.021) adjusted on, BMI, C-reactive protein, and D-dimer levels. VWF:CB levels could summarize both VWF increased levels and hyper-reactivity subsequent to ADAMTS13 overflow and, therefore, be a valuable and easy to perform clinical biomarker of microthrombosis and COVID-19 severity.