Clinical measurement of von Willebrand factor by fluorescence correlation spectroscopy.

BACKGROUND Identification of von Willebrand factor (vWF) abnormalities in a variety of conditions is hampered by the limitations of currently available diagnostic tests. Although direct multimer visualization by immunoelectrophoresis is a commonly used method, it is impractical as a routine clinical test. In this study, we used a biophysical analysis tool, fluorescence correlation spectroscopy (FCS), to measure vWF distributions. The goals were to develop a method that is quicker and simpler than vWF gel electrophoresis and to evaluate the potential of FCS as a clinical diagnostic technique. METHODS We analyzed plasma from 12 patients with type 1 von Willebrand disease (vWD), 14 patients with type 2 vWD, and 10 healthy controls using a fluctuation-based immunoassay approach. RESULTS FCS enabled identification and proper classification of type 1 and type 2 vWD, producing quantitative results that correspond to qualitative gel multimer patterns. FCS required minimal sample preparation and only a 5-min analysis time. CONCLUSIONS This study represents the first implementation of FCS for clinical diagnostics directly on human plasma. The technique shows potential for further vWF studies and as a generally applicable laboratory test method.