ADAMTS13 activity at different time points of the study. (A) Percentage of patients with normal (≥50%, green), moderately decreased (10% to <50%, red), or undetectable (<10%, blue) ADAMTS13 activity at day 30 and at months 3, 6, 9, 12, 15, 18, 21, and 24 (>80/92 patients available) after preemptive rituximab infusion. (B) ADAMTS13 activity (%) at day 0 (time of the first preemptive rituximab administration) and at different time points after the first infusion. Box plots represent quartiles, median, and range of the laboratory measurements. The blue line represents the variation of the mean over time. D, day; M, month.