ADAMTS13 activity during remission and risk of relapse. Serial samples were collected at 3-month intervals during clinical remission in patients with acquired TTP. Logistic regression analysis showed that lower ADAMTS13 activity was associated with a higher probability of relapse over the following 3 months. This relationship held true over different age groups, though younger age was also associated with a higher risk of relapse. Adapted from Jin et al,²⁶  with permission.