Longitudinal changes of plasma ADAMTS13 activity, antigen, and anti-ADAMTS13 IgG in 46 patients with iTTP. Each solid line depicts the change of plasma ADAMTS13 activity (A), ADAMTS13 antigen (B), and anti-ADAMTS13 IgG (C) over time (eg, on admission, 3-7 days after the initiation of TPE, and at clinical response/remission), as indicated in each panel. Mann-Whitney test was performed to determine the statistical difference between any 2 groups. Here, P < .0001 indicates that the difference is statistically highly significant.