ADAMTS13 and thrombotic thrombocytopenic purpura: Correct diagnosis is crucial because therapeutic decisions are based on this.11During the acute phase, an ADAMTS13 activity level below 10% was found in the patients' plasma (Fig. 1A) and could be ascribed to the presence of inhibitory anti-ADAMTS13 autoantibodies (Fig. 1E), resulting in the clear diagnosis of immune-mediated pregnancy-onset TTP.