ADAMTS-13 activity and von Willebrand factor levels in methylene-blue photo-inactivated plasma processed by either the Springe method or an 'in house' system.

BACKGROUND AND OBJECTIVES Methylene blue photo-inactivated plasma (MBPIP) has been reported to be less effective than fresh-frozen plasma (FFP) in the treatment of thrombotic thrombocytopenic purpura, which suggests a reduced content of the von Willebrand factor metalloprotease ADAMTS-13 in MBPIP. MATERIALS AND METHODS ADAMTS-13 activity and von Willebrand factor antigen (vWF:Ag) levels were measured in plasma before and after photo-oxidation by either the Springe method or a commercial 'in house' system as well as in cryoprecipitate-poor plasma (CPP) and FFP (20 units each). RESULTS Levels of ADAMTS-13 activity in MBPIP processed by the Springe method or the commercial 'in house' system were comparable to one another and did not significantly differ from levels found in FFP [median (range): 114% (57-139%), 99% (74-123%), and 106% (70-130%), respectively]. ADAMTS-13 activity was significantly reduced in CPP [median (range): 87% (70-107%) as compared with FFP (P < 0.05). Levels of vWF:Ag decreased after photo-oxidation by both methods. CONCLUSION In vitro ADAMTS-13 activity was conserved in MBPIP processed by the two photo-oxidation methods analysed and did not significantly differ from levels found in FFP.