Screening for inhibitors against vWF-cleaving protease in patient plasmas. NHP dilutions 1:20, 1:40, 1:80, 1:160, and 1:320 were used for calibration of the vWF-cleaving protease assay (A). Mixtures of equal volumes of NHP and patient plasmas were diluted with 9 vol of TBS/1 mmol/L Pefabloc and contained, accordingly, a 1:20 dilution each of normal and patient plasma (B).