ADAMTS13 and thrombotic thrombocytopenic purpura: Jin et al. analyzed 157 serial measures (in 24 patients) of ADAMTS13 activity and ADAMTS13 IgG antibodies and reported that while ADAMTS13 antibody levels were not significant predictors of relapse, lower ADAMTS13 activity (p = 0.03) and younger age (p = 0.02) were significant risk factors for TTP relapse and particularly sensitive and specific for relapse in the next 90 days (34).