Evaluation of an automated method for the quantification of von Willebrand factor antigen. Its application in the study of vascular dysfunction

Abstract

BACKGROUND AND OBJECTIVES: Abnormally high levels of von Willebrand factor (VWF) have been described as a response to physiologic and chronic alterations. It is therefore of great interest to have sensitive, accurate, fast and easy to use assays to quantify VWF. The aim of this study was to evaluate the performance characteristics of the immunoturbidimetric assay IL Test VWF:Ag and the use of this determination in the study of vascular dysfunction. DESIGN AND METHODS: The reproducibility, accuracy and linearity of the method were determined. A method comparison study was performed using an ELISA as the reference test. The assay reference range and its age-dependence were established. To evaluate the utility of the assay in vascular dysfunction, a cohort of 30 type 1 diabetes mellitus (DM) patients were analyzed, 11 of whom showed microvascular complications. RESULTS: The linearity range found was 10-150 IU/dL. Reported values above 150 IU/dL should be diluted and reanalyzed, expanding the range up to 600 IU/dL. The coefficients of variation were below 5% and inaccuracies below +/-15% within the linearity range. The comparison with the reference ELISA showed a good correlation coefficient (r = 0.985, VWF values from 5-680 IU/dl). The reference range was found to be 40.8 - 158.1 IU/dL. Significant differences between the DM type 1 patients with microvascular complications and a sex-age matched control group were observed. This difference was not observed for the DM patients not showing vascular alterations. INTERPRETATION AND CONCLUSIONS: The method is reproducible, accurate and linear. The assay correlates well with the reference ELISA. There is a relationship between patients showing microvascular diabetic complications and high levels of VWF:Ag. The assay is easy to perform, fully automated, and suitable for analyzing a small number of samples.