Anti-ADMATS13 antibody levels over the first month of follow-up after stopping PEX. The serial measurements of the median anti-ADAMTS13 IgG and inhibitor titer levels over the first 4 weeks after stopping PEX are shown. The anti-ADAMTS13 IgG levels are significantly lower in the prednisone-treated patients beginning in week 2, corresponding well to the improvement in ADAMTS13 activity. There was no statistically significant difference in the inhibitor titers between the 2 arms of the study.