Plasma DNA levels indicate the disease state of TTP patients during therapy. Analysis of serial plasma samples from patients of the investigational cohort. Time course of plasma DNA (black circles), ADAMTS13 activity (gray triangles), and platelet counts (open circles) of patients A through E with acute acquired TTP during PEX and corticosteroid therapy. The shaded area marks the time of PEX therapy. Samples with ADAMTS13 activity below 5% were plotted as 1/n.d. (not detected). Day 0 is the time of admission and start of therapy. Patient A (A) and patient B (B) represent a good outcome of PEX therapy. Platelet counts, ADAMTS13 activity, and plasma DNA levels normalized during therapy. (C) Patient C developed a catheter sepsis during therapy. Platelet counts and ADAMTS13 activity did not improve, and DNA levels increased during therapy. The patient died 10 days after admission. Patient D (D) and patient E (E) were refractory to PEX and developed 1 (E in panel D) and 3 (E1-E3 in panel E) exacerbations during therapy, respectively. Each exacerbation was associated with a decrease in platelet counts concomitant with an increase in circulating DNA. Both patients finally achieved remission either after additional therapy with rituximab (D) or after splenectomy (E). Reappearance of ADAMTS13 deficiency in patient E (E) 3 years after remission was not associated with thrombocytopenia or increases in plasma DNA. (1The x-axis not linearly formatted. Data shown are from consecutive plasma samples and the time between plasma sample collections varies. 2Rituximab was given 4 times at weekly intervals.)
