Kaplan-Meier curve of time to first relapse among 47 surviving patients with ADAMTS13 activity < 10% and among 136 patients with ADAMTS13 activity of 10% or more at the time of their initial diagnosis with TTP. Among the 47 surviving patients with ADAMTS13 activity < 10%, the 1 patient who has been lost to follow-up had a relapse before she refused further follow-up; therefore, data are complete for this analysis. The median follow-up for all 47 patients is 7.5 years. Median follow-up for the 26 living patients who have not relapsed is 4.6 years. (□), the 31 censored patients who have not relapsed: for 26 surviving patients, the time of last follow-up; for 5 patients, the time of death (competing event) before a relapse (event of interest) had occurred; deaths occurred at 0.3, 1.2, 3.5, 7.8, and 8.6 years. The Kaplan-Meier estimate of relapse at 7.5 years, the time of the last relapse (43%), is greater than the estimate using cumulative incidence methodology²⁷  to account for the competing events of death (41%). For the 136 patients with ADAMTS13 activity of 10% or more, median follow-up is 4.4 years. The Kaplan-Meier estimate of relapse at 1.5 years, the time of the last relapse (4%), is the same as the estimate using cumulative incidence methodology.²⁷