Evaluation Of Clinical Prognosis Of Immune Thrombotic Thrombocytopenic Purpura

BackgroundThrombotic thrombocytopenic purpura(TTP)is a potentially fatal thrombotic disease characterized by extensive microthrombosis in arterioles and capillaries,with an incidence of 3-10 cases per million people per year.The main features of TTP are severe thrombocytopenia and microangiopathic hemolytic anemia(MAHA).Some patients may have end-organ damage,such as cerebral infarction,renal insufficiency and myocardial infarction.The currently accepted theory for the pathogenesis of TTP is the deficiency of the von Willebrand factor(VWF)cleavage enzyme ADAMTS13(a disintegrin and metalloproteinase with thrombospondin type 1 motifs,13),which can be caused by the presence of antibodies against this enzyme or mutation of the gene encoding the enzyme,resulting in abnormal quality or quantity of ADAMTS13,namely immune thrombotic thrombocytopenic purpura(iTTP)and congenital thrombotic thrombocytopenic purpura(cTTP).Severe deficiency of AD AMTS 13 inhibits the cleavage of Ultra large von Willebrand factor released by vascular endothelial cells,leading to platelet aggregation and the formation of microthrombi in arterioles and capillaries.In recent years,with the improvement of the early diagnosis and the emergence of new treatment methods of TTP,the mortality rate in the acute episode has decreased significantly,from the previous 90%to 10%to 20%.However,we found that cTTP patients can remain asymptomatic for many years and some iTTP patients still have ADAMTS13 activity deficiency at clinical response.In addition,a second hit was needed for AD AMTS 13 knockout animals to develop TTP.Inflammation is the most common cause of TTP.Inflammation can lead to the activation of neutrophils and the formation of neutrophil extracellular traps.We speculate that neutrophil activation may be involved in the pathogenesis of TTP and may be associated with disease severity and prognosis.After treatment,most patients may achieve clinical response which is defined as platelet counts return to normal and lactate dehydrogenase levels lower than 1.5 times the upper limit of normal range.However,about 50%of patients still experience one or more courses of disease recurrence.Although the AD AMTS 13 deficiency is essential in the diagnosis of TTP,the guideline does not incorporate any AD AMTS 13 biomarkers into the criteria for treatment evaluation.There is currently no consensus on the relationship between AD AMTS 13 marker levels and risk of disease recurrence.Previous studies have attempted to determine the association of plasma AD AMTS 13 activity,antigen,inhibitor,immunoglobulin G or immune complex levels with disease recurrence and/or death in iTTP patients,but these studies may include some patients with approximately normal ADAMTS13 activity,or sufficient covariates were not included,or follow-up time was not included in the outcome analysis.So the results were one-sided.In view of the above,our study will comprehensively analyze the levels of neutrophil activation markers(S100A8/A9,citrullinated histone 3,histone/DNA complexes and cell-free DNA)in patients with iTTP and their relationship with organ dysfunction markers and disease severity.Besides,we will monitor the dynamic changes of ADAMTS13 markers(ADAMTS13 activity,antigens,and antiADAMTS13 IgG levels)during treatment in iTTP patients and evulate their role in predicting disease recurrence.ObjectivesThe present study aims to determine the association of neutrophil activation markers(S100A8/A9,citrullinated histone 3,histone/DNA complexes and cell-free DNA)with organ damage,disease severity and mortality and the role of longitudinal assessments of plasma ADAMTS13 biomarkers(ADAMTS13 activity,antigen,inhibitor and anti-ADAMTS 13 immunoglobulin G-type antibodies)in predicting immune thrombotic thrombocytopenia purpura(iTTP)exacerbation/relapse.Material and methods1.Plasma levels of neutrophil activation markers S100A8/A9,citrullinated histone H3(CitH3),histone/DNA complexes,and cell-free DNA(cfDNA)in a cohort of 108 acute episodes from 94 unique iTTP patients and healthy controls were determined and the association of each of these biomarkers with organ damage markers,disease severity and mortality were evaluated.2.Longitudinal plasma AD AMTS 13 biomarkers(ADAMTS13 activity,antigen and antiADAMTS13 immunoglobulin G-type antibodies)levels from eighty-three unique iTTP patients with 97 episodes were determined.The role of ADAMTS13 biomarkers at various clinical stages in predicting iTTP exacerbation/relapse were analyzed.Results1.Plasma levels of ADAMTS13 activity and antigen levels were increased with antiADAMTS13 IgG decreased when clinical response was achieved in iTTP patients.But not all patients recovered ADAMTS13 activity levels after treatment.Plasma levels of ADAMTS13 activity,antigen and anti-ADAMTS13 IgG on admission showed no significant value in predicting iTTP exacerbation or relapse.However,persistently low plasma AD AMTS 13 activity(<10 U/dL;hazard ratio[HR],4.4;95%confidence interval[CI],1.6-12.5;p=0.005)or high anti-ADAMTS13 IgG(HR,3.1;95%CI,1.27.8;p=0.016)3 to 7 days after the initiation of therapeutic plasma exchange was associated with an increased risk for exacerbation.Furthermore,low plasma ADAMTS13 activity(<10 IU/dL;HR,4.8;95%CI,1.8-12.8;p=0.002)and low ADAMTS13 antigen(<25th percentile;HR,3.3;95%CI,1.3-8.2;p=0.01)or high antiADAMTS13 IgG(>75th percentile;HR,2.6;95%CI,1.0-6.5;p=0.047)at clinical response or remission was also predictive of exacerbation.2.108 iTTP patients who received plasma exchange in the University of Alabama at Birmingham medical center from April 2006 to June 2019 were enrolled in this study,of whom 11 patients died in the acute episode.All acute iTTP patients had significantly increased plasma levels of S100A8/A9(median,84.8,interquartile range,IQR,31.2157.4 μg/mL),CitH3(median,3.8,IQR,2.2-6.4 ng/mL),histone/DNA complexes(median,55.7,IQR,35.8-130.8 U/mL),and cfDNA(median,937.7,IQR,781.3-1420.0 ng/mL)on the admission blood samples when compared with healthy controls.An increased plasma level of S100A8/A9,histone/DNA complex and cfDNA was associated with organ damage,coagulopathy and mortality in iTTP.Using receiver operating characteristic curve to determine the best cut-off value for each inflammatory marker to predict mortality.After being adjusted for age and history of hypertension,Cox proportional hazard regression analysis demonstrated that a hazard ratio(95%confidence interval)for the elevated plasma levels of S100A8/A9,histone/DNA complexes,and cfDNA to predict mortality was 11.5(1.4-90.9)(p=0.021),10.3(2.738.5)(p=0.001),and 12.8(3.9-42.0)(p=0.014),respectively.ConclusionsOur study demonstrate that neutrophil activation biomarkers such as S100A8/A9,histone/DNA complexes and cfDNA may help stratify patients with a high risk of death during acute iTTP episodes and intensive therapy strategy should be conducted in these patients as early as possible to reduce the mortality rate.Besides,neutrophil activation may play a role in the pathogenesis of iTTP.Our results also suggest the potential need for a more aggressive approach to achieve biochemical remission(ie,normalization of plasma ADAMTS13 activity,ADAMTS13 antigen,and anti-ADAMTS13 IgG)in patients with iTTP to prevent the disease recurrence.