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. 2019 Feb 13;14(2):e0211961. doi: 10.1371/journal.pone.0211961

Fig 2. Analytical characteristics of the active VWF assay.

Fig 2

(A) Binding of the VHH to R1306W VWF (●), R1306Q VWF (○), HVWF (σ), VWF in NPP under static conditions (π) and NPP after vortexing to simulate shear stress (▪, only 10x diluted). Dilution factors are indicated at the x-axis. (B) Mean active VWF levels in plasma pools (with low (91–110%), medium (150–200%) and high (>220%) active VWF levels) with corresponding SDs for 20 replicates on a single plate on the same day (intra-assay, white bars) or on 20 separate days (inter-assay, grey bars). (C) Recovery (%) of increasing levels of R1306W VWF spiked to plasma pool. The acceptance range of 90–110% of expected values is indicated by dotted lines. (D) Assay response (OD at 490 nm) for a 12-step, 1.2-fold dilution series of plasma spiked with R1306W. Linear regression parameters (±SD) are: slope 0,21 ± 0.006, intercept 0.03 ± 0.005, SD of residuals 0.007. (E) Low (L) and high (H) active VWF plasma pools were mixed in varying proportions to assess dilutional linearity. (F) Stability of active VWF in a plasma pool at baseline and after multiple freeze-thaw steps (Thaw 1–4). The acceptance criterium of <10% analyte loss is indicated by the dotted line. Data represent the mean±SD (n = 3) unless otherwise stated.