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Box plot showing the effect of repeated freezing and thawing on plasma concentrations of analytes. Lines on the box plot represent the median, 1st, and 3rd quartiles. Vertical lines represent the 10th and 90th centiles. IFN = interferon; IL = interleukin; MMP = matrix metalloproteinase; TNF = tumor necrosis factor; VEGF = vascular endothelial growth factor.
