Verification of a rapid von Willebrand factor propeptide assay

Background: Von Willebrand disease (VWD) is the most common inherited bleeding disorder caused by a deficiency or defect in von Willebrand factor (VWF). Quantitative defects include, type 1 VWD and type 3 VWD. Type 1 VWD is either due to decreased synthesis and secretion, or increased clearance of VWF. It is essential to diagnose individuals with increased VWF clearance, as treatment of these patients with 1-deamino-8-D-arginine vasopressin is not effective. Currently, there is one commercial assay that measures von Willebrand factor propeptide (VWFpp) levels. This assay is time consuming to perform. With this research we developed and verified a rapid assay to determine VWFpp levels in patient plasma. Methods: The commercial VWF mouse anti-human VWF propeptide matched antibody pair (clones CLB-Pro 35 and CLB-Pro 14.3) was used in enzyme-linked immunosorbent assays of the commercial and the rapid method. While the CLB-Pro commercial assay uses two-hour incubations, our rapid assay uses 30 minute incubations. We compared our assay to the CLB-Pro commercial assay using twenty type 1 VWD patient plasma. Two samples, the World Health Organization (WHO) 6th International Standard (IS) for factor VIII (FVIII)/VWF and a type 1 VWD patient with increased clearance were also tested four times in duplicate for five consecutive days to determine the inter- and intra-assay precision. Results: Our rapid assay showed equal sensitivity to the CLB-Pro commercial assay by detecting 1.5625% VWFpp. The intra- and interassay CVs of our assay were acceptable according to the Food and Drug Administration guideline of 2018. Conclusion: This rapid enzyme-linked immunosorbent assay (ELISA) is as sensitive and precise as the CLB-Pro commercial assay. Therefore, it can be used to rapidly diagnose patients with increased VWF clearance.

Plasma Level of von Willebrand Factor Propeptide at Diagnosis: A Marker of Subsequent Renal Dysfunction in Autoimmune Rheumatic Diseases

Introduction: Patients with systemic autoimmune rheumatic diseases (SARDs) such as rheumatoid arthritis, systemic lupus erythematosus (SLE), Sjögren syndrome, and systemic sclerosis, which are chronic inflammatory diseases, are prone to develop renal dysfunction, which is related to vascular endothelial cell damage. Material and Methods: We evaluated plasma levels of von Willebrand factor (VWF), VWF propeptide (VWF-pp), disintegrin-like and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), and VWF multimer pattern in patients with SARDs at diagnosis and investigated whether they may serve as markers to identify patients destined to develop renal dysfunction within 1 year. Renal dysfunction was defined as subsequent reduced estimated glomerular filtration rate (eGFR) by >25% or the new appearance of abnormal urine findings such as proteinuria (protein > 30 mg/dL) or hematuria (red blood cells >20/HPF in urine sediments). Overall, 63 patients with SARDs were studied. Results and Conclusions: We observed a significant increase of VWF-pp and a significant decrease of ADAMTS13 in patients with SARDs compared with normal healthy controls. The highest level of VWF-pp was observed in patients with SLE among the groups. The levels of VWF and multimer pattern of VWF were not different compared with normal healthy controls. Von Willebrand factor propeptide predicted a subsequent decrease in eGFR at a cutoff point of 210% (sensitivity, 78.6%; specificity, 73.5%) and new urinary abnormal findings at a cutoff point of 232% (sensitivity, 77.8%; specificity, 77.8%) Using these cutoff points, multivariable analysis revealed that VWF-pp was a significant risk factor for renal dysfunction at an odds ratio of 8.78 and 22.8, respectively, and may lead to a new therapeutic approach to prevent vasculitis and renal dysfunction.

Evaluation of the Utility of von Willebrand Factor Propeptide in the Differential Diagnosis of von Willebrand Disease and Acquired von Willebrand Syndrome

An increased von Willebrand factor propeptide (VWFpp) to VWF antigen (VWF:Ag) ratio (VWFpp/VWF:Ag) indicates an enhanced clearance of VWF. This finding has been described in von Willebrand disease (VWD) and in acquired von Willebrand syndrome (AVWS). A distinction between these two diseases, one congenital and the other acquired, is primarily based on family and personal history of bleeding. However, if this information is scanty, the diagnosis might be challenging due to the lack of an effective diagnostic biomarker. In this cross-sectional study, we assessed the ability of VWFpp/VWF:Ag for the differential diagnosis between VWD and AVWS. VWFpp/VWF:Ag was measured in a group of 153 patients (125 with VWD and 28 with AVWS). Most patients with AVWS and VWD showed an increased VWFpp/VWF:Ag, although to variable degrees. A marked increase of VWFpp/VWF:Ag was mainly associated with the diagnosis of AVWS and VWD type 1 Vicenza. A receiver operating characteristic curve was used to identify the optimal cutoff of VWFpp/VWF:Ag for discrimination of patients with a modestly increased (most VWD cases) versus those with a markedly increased clearance (AVWS and VWD type 1 Vicenza), and this cutoff was identified at the value of 3.9 (sensitivity: 0.70, specificity: 0.97). The ROC curve sorting from a logistic model containing VWFpp/VWF:Ag, age, and sex had an area under the curve (AUC) of 0.88 (95% confidence interval: 0.80–0.95). A subsequent molecular evaluation discriminated VWD type 1 Vicenza from AVWS. In conclusion, VWFpp/VWF:Ag appears helpful to discriminate patients with a markedly increase VWF clearance (AVWS or VWD type 1 Vicenza) from those with a modestly increased clearance (most VWD patients).