Clinical Significance Of ADAMTS13and VWF In Patients Following Hematopoietic Stem Cell Transplantation

Objective:To establish a stable method of ADAMTS13activity detecting.To observe the changes of ADAMTS13activity and von Willebrand factor (VWF) antigen in patients following hematopoietic stem cell transplantation (HSCT) in various periods. Then to analyze the changes and interaction between ADAMTS13and VWF in various periods, and to investigate the clinical significance of ADAMTS13and VWF in patients following HSCT.Methods:(1)Fluorescence resonance energy transfer substrate VWF73(FRETS-VWF73) assay was established to detect the plasma ADAMTS13activity in18patients with idiopathic thrombotic thrombocytopenic purpura (TTP).The residual collagen binding assay was used at the same time. Twenty-five healthy donors were enrolled into control group.(2) Patients:A total of113patients (66males,47females) receiving HSCT were investigated from Sep2010to Sep2011in our hospital. Median age is32(4-57) years old, including39cases with acute myeloid leukemia (AML),24cases with acute lymphoid leukemia (ALL),16cases with chronic myelogenous leukemia (CML),4cases with acute heterozygous cell leukemia (AHL),13cases with lymphoma,17cases with other diseases. According to the donor type,16cases received autologous transplantation,97cases received allogeneic transplantation (49cases from sibling matched donors,30cases from unrelated donor,10cases from partially matched family donors,9cases from umbilical cord blood stem cell transplantation). The modified BU/CY or TBI/CY was used for conditioning regimen in most patients, the BEAM or nonmyeloablative regimen was used in the rest cases.(2)Sample collection:The sodium citrate anticoagulated plasma was collected in patients following HSCT in various periods. The ADAMTS13activity and VWF antigen were detected with FRETS-VWF73and ELISA.(3)Statistical analysis:Using SAS9.3data was expressed as mean±standard deviation. Data different was analyzed using analysis of variance and t test. Rates were compared using chi-square test (X2). P<0.05was considered as significant difference. Logistic regression model was used for analysis of correlation. Statistical software is SAS9.3.Results:(1)Using FRETS-VWF73assay, the ADAMTS13activity in18patients with TTP was<10%,with an average level of (4.2±1.3)%, which is much less than the normal control group((77.0±48.0)%)(P<0.001). This result was basically consistent with residual collagen binding assay (ADAMTS13activity <5%).(2) The average values of ADAMTS13activity in113cases following HSCT at each period (before the transplantation pretreatment, after pretreatment, hematopoietic reconstitution and after hematopoietic reconstitution) were (45.1±30.6)%,(38.3±26.3)%,(43.5±29.5)%and (55.4±38.0)%. The ADAMTS13activity in each period were less than the normal controls (P<0.05). Moreover, compared with the stage before, the ADAMTS13activity in patients after transplantation conditioning was decreased (F=13.08, P=0.0004). The degree of ADAMTS13activity decreasing is different in the patients(less than30%in31cases(27.4%),30-60%in27cases(23.9%), over60%in9cases(8.0%)).The VWF antigen level in each period were (64.7±63.9)%,(114.7±103.0)%,(204.8±190.5)%and (207.8±189.1)%. The later three walues were higher than the normal control group (P<0.05). After the pretreatment, VWF antigen significant increased (F=16.45, P<0.0001) in patients than pretreatment before.(3) Thrombosis complications occurred in8patients, including veno-occlusive disease (VOD), thrombotic microangiopathies (TMA), pulmonary embolism(PE). The ADAMTS13activity after pretreatment (41.6±39.5)%were much less than pretreatment before(77.6±71.1)%(F=6.07,P=0.0432),while the VWF antigen (762.3±751.8)%was more than pretreatment before (1088.1±981.6)%. The ADAMTS13activity in3patients (37.5%) reduced more than60%in the stage after pretreatment while in patients without thrombosis reduced more than60%(9.0%)(X2=10.2458,P=0.0014). Logistic regression analysis showed that the ADAMTS13activity declined by more than60%is the risk of thrombosis (P=0.0065, OR=9.903,95%CI:1.899-51.644).(4) Acute graft-versus-host disease (aGVHD) occurred in49cases (50.5%) following allogeneic hematopoietic stem cell transplant.The median age was33(4-53) years old. According to the severity of aGVHD,23cases were classified as I degree,26cases as Ⅱ,Ⅲ,Ⅳ degree. The ADAMTS13activity before and after the pretreatment were (48.1±35.1)%,(46.4±30.4)%. Logistic regression analysis showed that the decreased ADMTS13activity after pretreatment not the risk factor for aGVHD (P=0.6737, OR=1.195,95%CI:0.522～2.732).The ADAMTS13activity in35patients was detected at the onset of aGVHD occurrence. The ADAMTS13activity in the stage of aGVHD occurs was less than the stage before pretreatment (F=22.34,P=0.0002). The ADAMTS13activity before pretreatment and aGVHD occurs were respectively (41.5±28.3)%and (22.7±19.9)%while the VWF antigen were (220.±216.7)%and (539.4±407.0)%.Conclusions:(1)The FRETS-VWF73assay is sensitive, reliable, quantitived and easy to operate. Using this method, the ADAMTS13activity can be. This method can be widely used as a routine test items in the TTP and some other patients.(2) The FRETS-VWF73assay shows that the ADAMTS13average activity level is lower than normal in the early stage of HSCT. The levels of ADAMTS13activity before pretreatment is lower than the level after pretreatment. Most of them reduced less than60%. With the reconstruction of the transplanted blood cells, plasma ADAMTS13activity began to rise.(3)The ADAMTS13activity of the patients with thrombosis reduced more than non-thrombotic group. The ADAMTS13activity more than60%is the risk factor of thrombotic complications. The ADAMTS13activity decreased after pretreatment is unrelated with aGVHD. The ADAMTS13activity decreased in the patients when aGVHD occurred. (4)VWF antigen increased in the course of transplantation. The VWF antigen in patients with thrombosis was already at a high level before transplantation.