Common VWF exon 28 polymorphisms in African Americans affecting the VWF activity assay by ristocetin cofactor

Veronica H. Flood, Joan Cox Gill, Patricia A. Morateck, Pamela A. Christopherson, Kenneth D. Friedman, Sandra L. Haberichter, Brian R. Branchford, Raymond G. Hoffmann, Thomas C. Abshire, Jorge A. Di Paola, W. Keith Hoots, Cindy Leissinger, Jeanne M. Lusher, Margaret V. Ragni, Amy D. Shapiro, Robert R. Montgomery