Thanks to Dr. Emmanuel Favaloro for pointing out an error in our April 29 post, “Quick Question Results, VWF Activity.” I (Geo) had transposed the principles of the VWF:GP1bR and VWF:GP1bM. I’ve corrected the error in the April 29 post–the correct principles are that VWF:GP1bR employs ristocetin, whereas VWF:GP1bM employs a gain-of-function form of GP1b that requires no ristocetin and is FDA-approved.
Dr. Favaloro adds, I’ve attached a table from my most recent review in STH: Favaloro EJ, Pasalic L, Curnow J. 100 years of von Willebrand disease: the journey to contemporary diagnostic pathways–an illustrative case-based narrative review. ” Semin Thromb Hemost. 2026 Mar 25. doi: 10.1055/a-2834-5520. PMID: 41881049). Feel free to post on Fritsma Factor if it helps….Emmanuel Favaloro.
Dr. Favaloro’s table is helpful, especially as he uses the indication VWF:GP1B for “VWF glycoprotein 1b-binding activity.” This terminology characterizes what we often term VWF:Ac (VWF activity). The activity we are measuring is more accurately described as VWF‘s platelet membrane GP1b binding capacity.
To further reduce confusion, Dr. Favaloro wrote, “Werfen markets VWF:GP1bR as a VWF:RCo assay, possibly inflating Fritsma Factor’s April survey numbers for the VWF:RCo. Perhaps VWF:GP1bR was marketed that way so Werfen could get FDA clearance as a VWF:RCo?
Fritsma Factor profits from Dr. Favaloro’s support as one of our panel of experts. His response often precedes others’ because the material posted in the evening in the US Central Daylight Time appears on his screen in Sydney, NSW, Australia, in the morning.
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