Evaluation of a new commercial method for von Willebrand factor multimeric analysis.

Abstract

Evaluation of von Willebrand factor (VWF) multimeric distribution is useful for subclassification of von Willebrand disease (VWD). Multimer analysis has historically been a manual, labor-intensive laboratory-developed test. The first commercial method for multimeric analysis was recently developed that utilizes a single instrument for gel electrophoresis, staining, and densitometry. The current study was undertaken to evaluate the performance characteristics of the new commercial method. Studies performed with the commercial method included evaluation of accuracy (method comparison), reference intervals (establishment of normal migration patterns in normal donor specimens), precision (multimer pattern reproducibility), and analytical sensitivity. In the method comparison studies, concordant interpretations were obtained in 19 of 24 comparisons, including normal and abnormal specimens. The 5 specimens with discordant interpretations all involved slight differences and none were considered clinically significant. Thirty-eight normal donor specimens demonstrated normal multimer patterns. Multimer pattern reproducibility was demonstrated in normal and abnormal controls tested on each gel. In the sensitivity studies, adequate visualization of multimers was determined to require VWF protein concentrations of approximately 5%-10% of normal. The commercial multimer method is a streamlined test that demonstrates comparable performance characteristics to our current laboratory-developed method and that provides the advantage of both electrophoresis gels and densitometry scans to aid interpretation.