Researchers seek better understanding of von Willebrand disease

The fidelity of diagnosis was another key finding to come out of ZPMCB-VWD. Most type 1 VWD cases were identified by low VWF:RCo. There was poor correlation between historical and current assays (r2 = 0.22), and diagnostic labs improved after central lab testing.

Next, Dr. Sidonio discussed findings from RENAWI 1 and 2, which are Italian registries of about 1,000 VWF patients that were organized by 12 centers in 2002. The goals are to evaluate the natural history of VWD in Italy and to characterize treatment strategies. According to preliminary findings from the researchers, the biological response to desmopressin (DDAVP) was 69% in those with VWD1, 26% in those with VWD2A, 20% in those with VWD2B, 33% in those with VWD2M, 71% in those with VWD2N, and 0% in those with VWD3 (Blood 2014;123:4037-44).

These researchers also found that a mean bleeding score of 3.5 corresponds to a VWF:RCo score of 30 U/dL or greater. “This indicates that there is something slightly different about patients that are above and below that threshold,” Dr. Sidonio said. “I think that’s something we’ve all been struggling with: trying to understand where the differences are and how aggressively we should be treating our patients with mild VWD.”

Another effort, The Willebrand in the Netherlands’ study (WiN), is a prospective cohort trial of about 700 patients with types 1, 2, and 3 VWD from 12 centers in that country (Blood 2008;112:4510). It was the first large study to use VWF propeptide (pp) to discriminate between severe type 1 and type 3 VWD. It also found that type 2 VWD is more characterized by increased clearance in VWF in contrast to type 1 VWD, leading to higher VWFpp/VWF:Ag ratio. In addition, in type 1 VWD, antigen rates increased about 3.5 U/dL per decade, RCo increased about 9.5 U/dL per decade, and Factor VIII: C increased about 7.1 U/dL per decade (J Thromb Haemost. 2014; 12[7]:1066-75).