ADAMTS13 inhibitor titer. Titer is shown in the acute phase (A) and in remission (B) in 32 surviving TMA patients. The level of ADAMTS13 activity in survivors at initial clinical remission defines 3 groups of TMA patients: below 5% (group 1, n = 13, black histograms), 15% to 40% (group 2, n = 12, dashed histograms), and 50% to 100% (group 3, n = 7, white histograms). The percentage of patients with either high, medium, low, or negative ADAMTS13 inhibitor titers within each group is presented both in the acute phase (A) and in remission (B). In group 1, ADAMTS13 inhibitor titers remained identical or decreased in remission when compared with the acute phase. In groups 2 and 3, all ADAMTS13 inhibitors, when present in the acute phase, disappeared in remission.