Follow-up of ADAMTS13 enzyme and its relationship with clinical events after allogeneic hematopoietic stem cell transplantation.

We aimed to evaluate the ADAMTS13 activity weekly after the hematopoietic stem cell transplantation and its relationship with clinical outcome. We studied 30 patients undergoing allogeneic hematopoietic stem cell transplantation with different conditioning regimens and 15 healthy controls. Plasmas were collected from patients 10 days before transplantation, the day of transplantation and 7th, 14th, 21st and 28th days after transplantation. Patients were followed for median period of 13 months (6-24 months). Patient plasmas were further collected when graft versus host disease (GVHD) developed. Enzyme activities of patients did not show a significant change through weeks [87% (39-145), 82% (16-110), 80% (36-134), 80% (36-134), 86% (47-127), 89% (11-127) and 90% (10-127)]. None of our patients had enzyme activity lower than 5% and had thrombotic microangiopathy, thromboembolism or hepatic veno-occlusive disease. Enzyme activity on the day of acute GVHD was not significantly different from the pretransplantation period (73 +/- 32 versus 87 +/- 20%, P = 0.231), but significantly lower than healthy controls (73 +/- 32 versus 97 +/- 16%, P = 0.02). Moreover, by the 28th day after transplantation, patients with acute GVHD had lower enzyme activity than the patients without acute GVHD (62 +/- 36 versus 95 +/- 22%, P = 0.009). ADAMTS13 activity was lower in samples taken from patients with chronic GVHD compared with baseline level (67 +/- 13 versus 91 +/- 30%, P = 0.15) and healthy controls (67 +/- 13 versus 97 +/- 16%, P = 0002). According to our data, transplantation does not have significant effect on ADAMTS13 activity. Acute or chronic GVHD causes a slight decrease of the enzyme that may indicate the possible cytokine effect.