Consensus on the standardization of terminology in thrombotic thrombocytopenic purpura and related thrombotic microangiopathies

Immature platelet dynamics correlate with ADAMTS13 deficiency and predict therapy response in immune-mediated thrombotic thrombocytopenic purpura

INTRODUCTION

Thrombotic thrombocytopenic purpura (TTP) requires prompt initiation of therapeutic plasma exchange (TPE) to avoid significant morbidity and mortality. ADAMTS13 activity testing defines TTP, however, at most institutions this is a send-out test and therapy is often initiated prior to measurement availability. We describe our experience looking at absolute immature platelet counts (A-IPC) in patients suspected with TTP at presentation and in response to therapy.

MATERIALS AND METHODS

Forty-eight patients treated for suspected TTP with A-IPC measure on admission and during hospitalization met inclusion criteria. Of these patients, sixteen had new-onset TTP (ADAMTS13 < 10%), ten were relapsing patients (first diagnosis prior to study period), and 22 were classified as non-TTP (ADAMTS13 ≥ 10%).

RESULTS

Patients with ADAMTS13 deficiency (TTP) had A-IPC different from those without deficiency. A-IPC of 1-2 × 10⁹/L at presentation had high sensitivity and specificity with a negative predictive value of 95.5 to 100%. Two-to-three-fold increases in A-IPC from count prior to TPE initiation was limited to ADAMTS13 deficient patients who was the group responding to therapy. Increases were higher in patients with new disease onset compared to relapsing patients (p = 0.018). Likewise, relapsing patients' A-IPC appeared dependent upon platelet count at time of relapse. A-IPC predicted and correlated with ADAMTS13 deficiency in new-onset TTP (p = 0.0002).

CONCLUSIONS

Only patients with A-IPC-fold increases responded to TPE with platelet count normalization. Our results represent a proof of concept that A-IPC measurements can supplement ADAMTS13 testing and determine response to TPE. Future studies are needed to establish ways to apply these findings in the setting of suspected TTP.

Absolute Immature Platelet Counts Suggest Platelet Production Suppression during Complicated Relapsing Thrombotic Thrombocytopenic Purpura

Absolute immature platelet counts (A-IPC) aid in diagnosis and treatment follow-up in thrombotic thrombocytopenic purpura (TTP). A-IPC was used to follow a patient on mycophenolate mofetil (MMF) maintenance therapy treated with a prolonged therapeutic plasma exchange (TPE) regimen for relapsing TTP. On admission, the platelet (PLT) count was 95 × 109/L declining to 14 × 109/L in 5 days. Daily TPE was initiated for suspected TTP, and MMF was discontinued. A-IPC and PLT count were 1 × 109/L and 14 × 109/L, respectively, prior to first TPE. A-IPC improved to 3.2 × 109/L with 1 TPE, and on day 5, A-IPC and PLT count were 7.5 × 109/L and 218 × 109/L, respectively. On day 6, A-IPC and PLT count decreased to 4.8 × 109/L and 132 × 109/L further worsening to 0.4 × 109/L and 13 × 109/L, respectively. ADAMTS13 activity remained <5% with an inhibitor; counts did not recover. Initial improvement followed by rapidly declining A-IPC despite therapy suggested production suppression. In TTP, A-IPC may aid in establishing early therapy effects over PLT production.

Insights from the Hereditary Thrombotic Thrombocytopenic Purpura Registry: Discussion of Key Findings Based on Individual Cases from Switzerland

The Hereditary TTP Registry is an international cohort study for patients with a confirmed or suspected diagnosis of hereditary thrombotic thrombocytopenic purpura (hTTP) and their family members. Hereditary TTP is an ultra-rare blood disorder (prevalence of ∼1-2 cases per million), the result of autosomal-recessively inherited congenital ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency (ADAMTS13 activity <10% of the normal), and associated with yet many unanswered questions. Until December 2017, the Hereditary TTP Registry had enrolled 123 confirmed hTTP patients. Their median age at disease onset was 4.5 years (range: 0-70) and at clinical diagnosis 16.7 years (range: 0-69), a difference that highlights the existing awareness gap in recognizing hTTP. The systematic collection of clinical data of individual patients revealed their substantial baseline comorbidities, as a consequence of recurring TTP episodes in the past. Most notable was the high proportion of patients having suffered from premature arterial thrombotic events, mainly transient ischemic attacks, ischemic strokes, and to a lesser extent myocardial infarctions. At 40 to 50 years of age and above, more than 50% of patients had suffered from at least one such event, and many had experienced arterial thrombotic events despite regular plasma infusions every 2 to 3 weeks that supplements the missing plasma ADAMTS13. The article by van Dorland et al. (Haematologica 2019;104(10):2107-2115) and the ongoing Hereditary TTP Registry cohort study were recognized with the Günter Landbeck Excellence Award at the 50th Hemophilia Symposium in Hamburg in November 2019, the reason to present the Hereditary TTP Registry in more detail here.

Reduced sensitivity of PLASMIC and French scores for the diagnosis of thrombotic thrombocytopenic purpura in older individuals

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder characterized by thrombocytopenia, microangiopathic hemolysis, and ischemic organ failure. The PLASMIC and French TTP scores can help guide clinical decisions when ADAMTS13 testing is not immediately available. Older individuals often present atypically, but the impact of age on these tools is not known.

STUDY DESIGN AND METHODS

We calculated the sensitivity and specificity of the PLASMIC and French TTP scores in patients enrolled in the Johns Hopkins thrombotic microangiopathy (TMA) registry.

RESULTS

Of 257 patients with TMA enrolled in the registry, we excluded patients less than 18 years of age (n = 19), with prior TMA (n = 81) or who initially presented at another hospital (n = 25). The remaining 132 patients (75 with TTP and 57 with other TMA) were analyzed. Sensitivity of a French score of 2 decreased with age and was 72.2%, 61.5%, and 46.2% for ages 18 to 39, 40 to 59, and ≥ 60 years old, respectively. A PLASMIC score ≥ 5 had higher sensitivity than the French score but this also decreased with age; sensitivity was 91.4% (95% confidence interval [CI], 76.9-98.2), 78.3% (95% CI, 56.3-92.5), and 76.9% (95% CI, 46.2-95.0) for patients 18 to 39, 40 to 59, and ≥ 60 years old, respectively. Older patients had higher platelet counts and serum creatinine than the youngest group, contributing to the loss in sensitivity.

CONCLUSION

The PLASMIC and French TTP scores have reduced sensitivity at age ≥ 60 years and are less reliable in identifying TTP in older patients. A high index of suspicion and availability of rapid ADAMTS13 assays is required to correctly diagnose all patients with TTP.

Exome Sequencing Identifies Abnormalities in Glycosylation and ANKRD36C in Patients with Immune-Mediated Thrombotic Thrombocytopenic Purpura

BACKGROUND

 Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal blood disorder, resulting from autoantibodies against ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13). However, the mechanism underlying anti-ADAMTS13 autoantibody formation is not known, nor it is known how genetic aberrations contribute to the pathogenesis of iTTP.

METHODS

 Here we performed whole exome sequencing (WES) of DNA samples from 40 adult patients with iTTP and 15 local healthy subjects with no history of iTTP and other hematological disorders.

RESULTS

 WES revealed variations in the genes involved in protein glycosylation, including O-linked glycosylation, to be a major pathway affected in patients with iTTP. Moreover, variations in the ANKRD gene family, particularly ANKRD36C and its paralogs, were also more prevalent in patients with iTTP than in the healthy controls. The ANKRD36 family of proteins have been implicated in inflammation. Mass spectrometry revealed a dramatic alternation in plasma glycoprotein profile in patients with iTTP compared with the healthy controls.

CONCLUSION

 Altered glycosylation may affect the disease onset and progression in various ways: it may predispose patients to produce ADAMTS13 autoantibodies or affect their binding properties; it may also alter clearance kinetics of hemostatic and inflammatory proteins. Together, our findings provide novel insights into plausible mechanisms underlying the pathogenesis of iTTP.

Inhibitory anti ADAMTS13 antibodies with a new rapid fully automated CLiA assay

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder characterized by severe ADAMTS13 deficiency. The acquired form is associated with autoantibodies directed against ADAMTS13. Both noninhibitory and inhibitory autoantibodies can be detected by ELISA assay, while only inhibitory autoantibodies are detected by Bethesda assay. Due to its short TAT and good performance, chemiluminescence (CliA) ADAMTS13 activity (HemosIL Acustar) has proven to be a good choice in the diagnosis of TTP in emergency settings. Aim of this study was to analyse the performance of the CliA ADAMTS13 activity assay in detecting inhibitory ADAMTS13 antibodies using the Bethesda assay.

METHODS

A method comparison study was performed on 69 stored samples: 11 acute TTPs, 38 TTP follow-ups, 5 TTP relapses, 1 congenital TTP, 10 HUS, 4 suspected TTPs. We retrieved the results of tests previously run in ELISA for both activity and autoantibodies. At the same time, we reran new tests including ELISA and CliA activity, ELISA autoantibodies, and ELISA and CliA Bethesda assays on thawed frozen samples.

RESULTS

Very good correlation was observed between ELISA and CliA activity assay results (r = 0.96) and between archived ELISA and CliA activity results (r = 0.93). Agreement between the anti-ADAMTS13 assays ranged from good (k = 0.63) to very good (k = 0.92).

CONCLUSIONS

CliA and ELISA Bethesda assays showed very good agreement with samples run at the same time using ELISA ADAMTS13-autoantibody assay. Albeit more expensive, the CliA Bethesda assay identified inhibitory anti-ADAMTS13 within almost the same TAT as ELISA, but with better automation and limited operator involvement.

Complement in Secondary Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) is a condition characterized by thrombocytopenia and microangiopathic hemolytic anemia (MAHA) with varying degrees of organ damage in the setting of normal international normalized ratio and activated partial thromboplastin time. Complement has been implicated in the etiology of TMA, which are classified as primary TMA when genetic and acquired defects in complement proteins are the primary drivers of TMA (complement-mediated TMA or atypical hemolytic uremic syndrome, aHUS) or secondary TMA, when complement activation occurs in the context of other disease processes, such as infection, malignant hypertension, autoimmune disease, malignancy, transplantation, pregnancy, and drugs. It is important to recognize that this classification is not absolute because genetic variants in complement genes have been identified in patients with secondary TMA, and distinguishing complement/genetic-mediated TMA from secondary causes of TMA can be challenging and lead to potentially harmful delays in treatment. In this review, we focus on data supporting the involvement of complement in aHUS and in secondary forms of TMA associated with malignant hypertension, drugs, autoimmune diseases, pregnancy, and infections. In aHUS, genetic variants in complement genes are found in up to 60% of patients, whereas in the secondary forms, the finding of genetic defects is variable, ranging from almost 60% in TMA associated with malignant hypertension to less than 10% in drug-induced TMA. On the basis of these findings, a new approach to management of TMA is proposed.

The HLA Variant rs6903608 Is Associated with Disease Onset and Relapse of Immune-Mediated Thrombotic Thrombocytopenic Purpura in Caucasians

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare, life-threatening thrombotic microangiopathy caused by severe ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin motifs 13) deficiency, recurring in 30–50% of patients. The common human leukocyte antigen (HLA) variant rs6903608 was found to be associated with prevalent iTTP, but whether this variant is associated with disease relapse is unknown. To estimate the impact of rs6903608 on iTTP onset and relapse, we performed a case-control and cohort study in 161 Italian patients with a first iTTP episode between 2002 and 2018, and in 456 Italian controls. Variation in rs6903608 was strongly associated with iTTP onset (homozygotes odds ratio (OR) 4.68 (95% confidence interval (CI) 2.67 to 8.23); heterozygotes OR 1.64 (95%CI 0.95 to 2.83)), which occurred over three years earlier for each extra risk allele (β −3.34, 95%CI −6.69 to 0.02). Of 153 survivors (median follow-up 4.9 years (95%CI 3.7 to 6.1)), 44 (29%) relapsed. The risk allele homozygotes had a 46% (95%CI 36 to 57%) absolute risk of relapse by year 6, which was significantly higher than both heterozygotes (22% (95%CI 16 to 29%)) and reference allele homozygotes (30% (95%CI 23 to 39%)). In conclusion, HLA variant rs6903608 is a risk factor for both iTTP onset and relapse. This newly identified biomarker may help with recognizing patients at high risk of relapse, who would benefit from close monitoring or intensified immunosuppressive therapy.

A critical evaluation of caplacizumab for the treatment of acquired thrombotic thrombocytopenic purpura

Introduction: Acquired thrombotic thrombocytopenic purpura (aTTP) is a thrombotic microangiopathy caused by inhibitory autoantibodies against ADAMTS13 protein. Until recently, the combination of plasma exchange (PEX) and immunosuppression has been the standard front-line treatment in this disorder. However, aTTP-related mortality, refractoriness, and relapse are still a matter of concern. Areas covered: The better understanding of the pathophysiological mechanisms of aTTP has allowed substantial improvements in the diagnosis and treatment of this disease. Recently, the novel anti-VWF nanobody caplacizumab has been approved for acute episodes of aTTP. Caplacizumab is capable to block the adhesion of platelets to VWF, therefore inhibiting microthrombi formation in the ADAMTS13-deficient circulation. In this review, the characteristics of caplacizumab together with the available data of its efficacy and safety in the clinical setting will be analyzed. Besides, the current scenario of aTTP treatment will be provided, including the role of other innovative drugs. Expert opinion: With no doubt, caplacizumab is going to change the way we treat aTTP. In combination with standard treatment, caplacizumab can help to significantly reduce aTTP-related mortality and morbidity and could spare potential long-term consequences by minimizing the risk of exacerbation.

Optimization of the detection of inhibitory autoantibodies against the VWF-cleaving protease ADAMTS13 with an automated chemiluminescent ADAMTS13 activity immunoassay

INTRODUCTION

Acquired thrombotic thrombocytopenic purpura is a rare disease associated with the production of autoantibodies against the VWF-cleaving protease ADAMTS13. The detection of these antibodies is made difficult by the instability of ADAMTS13 in citrated plasma and the time-consuming ADAMTS13 assays. The aim of our study was to evaluate the optimal conditions for detecting anti-ADAMTS13 inhibitory antibodies with the novel automated chemiluminescent immunoassay HemosIL^R AcuStar ADAMTS13 Activity assay.

METHODS

The parallelism between the AcuStar ADAMTS13 calibration curve and ADAMTS13 concentrations in serially diluted citrated plasma was evaluated after 2 hours incubation at 25°C, 37°C, or 37°C after addition of Ca²⁺ to preserve the activity of the metalloprotease. Using Bethesda assays based on the 3 incubation procedures and the HemosIL^R AcuStar ADAMTS13 Activity assay, the inhibitor titers were determined in patients' samples with ADAMTS13 antibodies and compared with those determined using the Technozym^R ADAMTS13 activity ELISA.

RESULTS

The criterion of parallelism was respected for the 3 incubation methods over the range of ADAMTS13 concentrations relevant for the detection of ADAMTS13 inhibitor antibodies in a Bethesda assay. In agreement with this observation, all the incubation methods permitted the accurate detection and quantification of inhibitory anti-ADAMTS13 antibodies in the samples from patients with acquired thrombotic thrombocytopenic purpura.

CONCLUSION

Incubation of plasma samples with normal plasma at 25°C, 37°C, or 37°C after addition of Ca²⁺ can be used in a Bethesda assay for quantifying the inhibitory activity of antibodies interfering with ADAMTS13 in the chemiluminescent HemosIL^R AcuStar ADAMTS13 Activity assay.

Good practice statements (GPS) for the clinical care of patients with thrombotic thrombocytopenic purpura

BACKGROUND

Despite advances in treatment options for thrombotic thrombocytopenic purpura (TTP), there are still limited high quality data to inform clinicians regarding its management.

METHODS

In June 2018, the ISTH formed a multidisciplinary guideline panel to issue recommendations about treatment of TTP. The panel discussed 12 treatment questions related to both immune-mediated TTP (iTTP) and hereditary/congenital TTP (cTTP). The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including evidence-to-decision frameworks, to appraise evidence and formulate recommendations.

RESULTS

The panel agreed on eleven recommendations based on evidence ranging from very low to moderate certainty. For first episode and relapses of acute iTTP, the panel made a strong recommendation for the addition of corticosteroids to therapeutic plasma exchange (TPE), and a conditional recommendation for addition of rituximab and caplacizumab. For asymptomatic iTTP with low ADAMTS13, the panel made a conditional recommendation for rituximab outside of pregnancy, and for prophylactic TPE during pregnancy. For asymptomatic cTTP, the panel made a strong recommendation for prophylactic plasma infusion during pregnancy, but a conditional recommendation for plasma infusion or a wait and watch approach outside of pregnancy.

CONCLUSIONS

The panel's recommendations are based on all the available evidence for the treatment effects of various approaches including suppressing inflammation, blocking platelet clumping, replacing the missing and/or inhibited ADAMTS13, and suppressing ADAMTS13 antibody production. There was insufficient evidence for further comparison of different treatment approaches, for which future high-quality studies in iTTP (e.g., rituximab, corticosteroids, recombinant ADAMTS13, and caplacizumab) and in cTTP (eg, recombinant ADAMTS13) are needed.

Development and validation of a prediction model (AHC) for early identification of refractory thrombotic thrombocytopenic purpura using nationally representative data

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening haematological emergency. Although therapeutic plasma exchange together with corticosteroids achieve successful outcomes, a considerable number of patients remain refractory to this treatment and require early initiation of intensive therapy. However, a method for the early identification of refractory iTTP is not available. To develop and validate a model for predicting the probability of refractory iTTP, a cohort of 265 consecutive iTTP patients from 17 large medical centres was retrospectively identified. The derivation cohort included 94 patients from 11 medical centres. For the validation cohort, we included 40 patients from the other six medical centres using geographical validation. An easy-to-use risk score system was generated, and its performance was assessed using internal and external validation cohorts. In the multivariable logistic analysis of the derivation cohort, three candidate predictors were entered into the final prediction model: age, haemoglobin and creatinine. The prediction model had an area under the curve of 0.886 (95% CI: 0.679-0.974) in the internal validation cohort and 0.862 (95% CI: 0.625-0.999) in the external validation cohort. The calibration plots showed a high agreement between the predicted and observed outcomes. In conclusion, we developed and validated a highly accurate prediction model for the early identification of refractory iTTP. It has the potential to guide tailored therapy and is a step towards more personalized medicine.

ISTH guidelines for the diagnosis of thrombotic thrombocytopenic purpura

BACKGROUND

Despite an increase in our understandings of pathogenesis of thrombotic thrombocytopenic purpura (TTP), the approaches for initial diagnosis and management of TTP vary significantly.

OBJECTIVE

The evidence-based guidelines of the International Society on Thrombosis and Haemostasis (ISTH) are intended to support patients, clinicians, and other health care professionals in their decisions about the initial diagnosis and management of acute TTP.

METHODS

In June 2018, ISTH formed a multidisciplinary panel that included hematologists, an intensive care physician, nephrologist, clinical pathologist, biostatistician, and patient representatives, as well as a methodology team from McMaster University. The panel composition was designed to minimize the potential conflicts of interests. The panel used the Grading of Recommendations Assessment, Development, and Evaluation approach and the Population, Intervention, Comparison, Outcome framework to develop and grade their recommendations. Public comments were sought and incorporated in the final document.

RESULTS

The panel agreed on three recommendations covering the initial diagnosis with emphasis on the importance of ADAMTS13 testing (eg, activity, anti-ADAMTS13 IgG or inhibitor) and assessment of the pretest probability of TTP by clinical assessment and/or the risk assessment models like the PLASMIC or French score. The panel noted how availability and turnaround time of ADAMTS13 test results might affect early diagnosis and management, in particular the use of caplacizumab.

CONCLUSIONS

There is a lack of high-quality evidence to support strong recommendations for the initial diagnosis and management of a suspected TTP. The panel emphasized the importance of obtaining ADAMTS13 testing in a proper clinical context. Future research should focus on how to monitor and act on ADAMTS13 levels during remission.

Assessment and Monitoring of Patients with Immune-Mediated Thrombotic Thrombocytopenic Purpura (iTTP): Strategies to Improve Outcomes

Background

Acquired or immune-mediated TTP (iTTP) is a life-threatening thrombotic microangiopathy, characterized by the presence of microangiopathic hemolytic anemia and severe thrombocytopenia, and a variable degree of ischemic organ damage, related to a severe deficiency of ADAMTS13, which is a serine metalloprotease necessary for cleavage of large vWF multimers. There has been a dramatic decrease in mortality rates with the recognition of the pathophysiology of iTTP over the years. Although therapeutic plasma exchange (TPE) together with corticosteroids are the backbone of the upfront treatment of patients with iTTP with successful outcomes, patients may remain refractory and/or relapse following an initial response to this treatment.

Methods

We performed a review regarding the pathogenesis, diagnosis, treatment strategies, monitoring, and prognosis of iTTP.

Results

There are several new treatment strategies, which can be used among these patients, helping in improving outcomes of iTTP. Rituximab has been shown to be a safe and effective adjunct to TPE, especially in patients with refractory and/or relapse as well as it is increasingly used preemptively to prevent exacerbation or recurrence. Recently, caplacizumab, a nanobody targeting vWF, was approved as an addition to the current regimen of TPE and immunomodulation for patients of iTTP.

Conclusion

Specific predictors of relapse in patients in remission can be relevant for an optimal patient management. Different models including ADAMTS13 biomarkers can provide a new screening strategy to identify patients who may predict outcomes and the risk of relapse, benefit from preemptive therapy prior to relapse.

Rituximab prolongs the time to relapse in patients with immune thrombotic thrombocytopenic purpura: analysis of off-label use in Japan

Immune thrombotic thrombocytopenic purpura (iTTP) is caused by ADAMTS13 deficiency due to anti-ADAMTS13 autoantibodies. Rituximab, an anti-CD20 monoclonal antibody, is often used to suppress these autoantibodies. This retrospective study, conducted in an iTTP cohort in Japan, evaluated the long-term efficacy of rituximab as off-label treatment for refractory or relapsed cases. A total of 252 iTTP patients with severe ADAMTS13 deficiency (< 10%) and its inhibitor were enrolled, and 169 episodes in 156 patients were analyzed. Sixty-five episodes with relapse or resistance to conventional treatment were treated with rituximab, while 104 episodes received conventional treatment only. The rituximab group had a significantly higher inhibitor titer than the rituximab-untreated group. During the median follow-up period of 3.9 years, there were 8 relapses in the rituximab group and 17 relapses in the rituximab-untreated group. The median time to relapse in the rituximab group (2.9 years) was significantly longer than that in the rituximab-untreated group (1.2 years). Relapse-free survival at 2 years was significantly higher in the rituximab group than in the rituximab-untreated group. The incidence of relapse at 5 years did not differ between the 2 groups. Rituximab reduced the risk of relapse in refractory or relapsed iTTP patients for 2 years.

Immune-mediated thrombotic thrombocytopenic purpura in patients with and without systemic lupus erythematosus: a retrospective study

Background

Thrombotic thrombocytopenic purpura (TTP) is associated with more deleterious outcomes in patients with systemic lupus erythematosus (SLE). However, ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) levels and ADAMTS13 inhibitor were not routinely assayed in most previous studies. The objective of this study is to compare the characteristics and outcomes of immune-mediated TTP (iTTP) in patients with and without SLE.

Methods

The medical data of 28 patients with iTTP from Peking Union Medical College Hospital were analysed. ADAMTS13 activity and ADAMTS13 inhibitor were measured in all patients.

Results

All 28 patients had ADAMTS13 inhibitor and severe ADAMTS13 deficiency. iTTP was considered SLE-related (SLE-TTP) in 10 patients and primary (primary iTTP) in 18 patients. Renal involvement on presentation was more severe in patients with primary iTTP as determined by higher serum creatinine (162.7 ± 110.6 vs 73.3 ± 13.4 μmol/L, p < 0.01) and more prevalent acute kidney injury (72.2% vs 10.0%, p < 0.01) than in patients with SLE-TTP. More patients with SLE-TTP were treated with steroid pulse therapy (90.0% vs 16.7%, p < 0.01) and intravenous immunoglobulin (IVIG) (50.0% vs 5.6%, p = 0.01) compared to patients with primary iTTP. After adjustments for age and treatment, including steroid pulse therapy and IVIG treatment, the likelihood of clinical remission of SLE-TTP was significantly increased compared to that of primary iTTP (HR 7.6 [1.2, 50.1], p = 0.03). Mortality was also lower among patients with SLE-TTP than among patients with primary iTTP (0 vs 38.9%, p = 0.03).

Conclusions

Renal involvement was less severe in patients with SLE-TTP than in patients with primary iTTP. The treatment responses and outcomes of SLE-TTP were no worse and perhaps even better than those of primary iTTP. When TTP is diagnosed in SLE patients, the ADAMTS13 level and ADAMTS13 inhibitor profile should be considered in addition to clinical features.

Podocyte Involvement in Renal Thrombotic Microangiopathy: A Clinicopathological Study

BACKGROUND

The current study aimed to evaluate the associations between podocyte injury and clinicopathological features in renal thrombotic microangiopathy (TMA) based on a Chinese cohort, which might be underscored in this disease.

METHODS

The clinical, laboratory, and renal histopathological data of patients with renal biopsy-proven TMA from 2000 to 2015 in our institute were collected. Foot process effacement (FPE) was quantified by foot process width (FPW) by electron microscopy. Podocytes in the renal specimens were also detected by stainings for podocyte-specific markers, including Wilms tumor 1 (WT-1), synaptopodin, and podocalyxin. The associations between FPW and clinico-histopathological data were further analyzed. A composite end-point was defined by all-cause death or end-stage renal disease to address the predictive value of FPW.

RESULTS

Sixty-three patients with renal biopsy-proven TMA were enrolled. The FPW of renal TMA patients was 1,090 ± 637 nm (range, 572-4,748 nm), which was significantly higher than the normal range in our center (p = 0.005). By immunohistochemistry and immunofluorescence assays, we found decreased expressions of synaptopodin, podocalyxin, and WT-1 and continued stainings of WT-1 in some podocytes without detectable synaptopodin stainings in the areas of sclerotic tufts and cellular crescents. The FPW value was correlated with the serum albumin concentration (rs = -0.281, p = 0.026), proteinuria amount (rs = 0.255, p = 0.047), serum creatinine levels (rs = 0.339, p = 0.007), and eGFR (rs = -0.335, p = 0.007). According to ROC curve analysis, the optimal cutoff level of FPW for predicting the composite end-point was 869 nm. In patients with FPW ≥ 869 nm, FPW levels were further correlated with the severity of mesangiolysis (rs = 0.351, p = 0.033) and glomerulosclerosis (rs = 0.369, p = 0.025) in pathological evaluations. Patients without clinical remission also had higher FPW than those with remission (1,240 ± 793 vs. 925 ± 344 nm, p = 0.013). The multivariate Cox hazard model showed that FPW ≥ 869 nm was an independent risk factor for the composite end-point (hazard ratio: 3.64, 95% CI: 1.37-9.66, p = 0.009).

CONCLUSION

The podocyte injury was prevalent and the FPW levels were closely associated with clinicopathological features, especially prognosis, in renal TMA patients.

Successful treatment of refractory thrombotic thrombocytopenic purpura associated with systemic lupus erythematosus with combination of plasma exchange and low-dose rituximab

OBJECTIVES

Thrombotic thrombocytopenia purpura (TTP) associated with systemic lupus erythematous (SLE) (i.e., SLE-TTP) is a rare life-threatening disease often requiring intensive immunosuppressive agents, in addition to high-dose corticosteroids and plasma exchange (PEX). The optimal therapy of rituximab is unclear, but 375 mg/m² weekly for 4 weeks is the usual practice, adopted from regimens for non-Hodgkin's lymphoma. We reported two cases of refractory SLE-TTP that showed good efficacy and prognosis with combination of methylprednisolone (MP) pulse, plasma exchange and low-dose rituximab (100 mg weekly for 4 weeks) treatment.

METHODS

Clinical data and treatment outcomes were reviewed of two patients diagnosed with refractory SLE-TTP at Peking Union Medical College Hospital between July 2017 and July 2018.

RESULTS

Both patients had SLE and presented with microangiopathic anemia and thrombocytopenia. Laboratory assays revealed high anti-nuclear antibody titers, reduced complement 3 and 4 levels, proteinuria, significantly elevated lactate dehydrogenase, schistocytes on peripheral blood smear, low ADAMTS13 activity, and the presence of ADAMTS13 inhibitor. In both patients, platelet counts remained below 50 × 10⁹/L after MP pulse and 6 PEXs, confirming the diagnosis of refractory SLE-TTP. Low-dose rituximab (100 mg weekly for 4 weeks) was administered in both cases, resulting in normalization of platelet counts and significant reductions in B-lymphocyte counts. No TTP relapse or SLE flare occurred during 24 months of follow-up.

CONCLUSIONS

Our cases confirmed the efficacy and good follow-up outcomes of low-dose rituximab treatment (100 mg weekly for 4 weeks) for refractory SLE-TTP.

Idiopathic TTP in the Middle East: Epidemiology and clinical outcomes in infection associated episodes

INTRODUCTION

Literature on epidemiology of thrombotic thrombocytopenic purpura (TTP) in the Middle East is scarce.

MATERIALS AND METHODS

We prospectively examined the association between infection and clinical outcomes in 44 patients with idiopathic TTP, with severely deficient ADAMTS13. We also investigated seasonality of the disease, hoping to better understand the epidemiology of idiopathic TTP.

RESULTS

Summer demonstrated significantly lower incidence for idiopathic TTP, compared with other seasons P = 0.0003. Fourteen patients had 15 episodes with a suspected concomitant infection. Five initial episodes were triggered by an infection (33.3 %), all presenting in winter, six episodes were associated with an exacerbation (40 %) and infection triggered a relapse in the other four episodes (26.7 %), with 2 episodes presenting in winter. TTP associated infections included: central line infection, urinary tract infection and post-operative infection. One patient had respiratory tract infection, on both his initial and relapsing episodes. Refractoriness to treatment was demonstrated in 4 patients (28.6 %) and it was associated with dental abscess (one patient), septic shock (one patient) and Mycoplasma pneumonia (2 patients). All 4 patients had markedly elevated CRP values with a median of 335 mg/L.

CONCLUSION

Most of the infection associated episodes developed in winter (77.8 %). In patients with idiopathic TTP refractory to conventional treatment, infection should be seriously considered as an additional contributing factor for their initial and /or recurrent episodes, particularly when CRP is markedly elevated.

Clinical Problem Solving and Using New Paths in the Laboratory: Learning from Case Studies

Three selected casuistic studies of individual patient problems from my long-standing professional experience are presented. I intend to highlight the potential contribution of case studies, including new approaches of laboratory investigation, for the advancement of pathophysiological knowledge and would encourage to “rehabilitate” the low academic profile generally attributed to “case reports.”

Diagnostic accuracy of the PLASMIC score in patients with suspected thrombotic thrombocytopenic purpura: A systematic review and meta-analysis

BACKGROUND

The PLASMIC score was developed to identify patients with thrombotic microangiopathy who are most likely to have immune thrombotic thrombocytopenic purpura (TTP) and benefit from therapeutic plasma exchange (TPE). PLASMIC scores of 0-4, 5, and 6-7 are said to correspond to low, intermediate, and high probability of TTP, respectively.

STUDY DESIGN AND METHODS

We conducted a systematic review and meta-analysis on the diagnostic accuracy of the PLASMIC score in adults with suspected TTP. We evaluated the sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of PLASMIC score thresholds of ≥5 and ≥6. Study quality was appraised using the QUADAS-2 tool.

RESULTS

We identified 13 eligible studies, which collectively enrolled 970 patients. The median prevalence of TTP among eligible studies was 35%. The sensitivity and specificity of a PLASMIC score ≥5 was 0.99 (95% confidence interval [CI], 0.91-1.00) and 0.57 (95% CI, 0.41-0.72), respectively. At a prevalence of 35%, the NPV of a PLASMIC score ≥5 was 0.99 (95% CI, 0.92-1.00). A PLASMIC score ≥6 was associated with a sensitivity and specificity of 0.85 (95% CI, 0.67-0.94) and 0.89 (95% CI, 0.81-0.94), respectively. The NPV of a PLASMIC score ≥6 at a prevalence of 35% was 0.92 (95% CI, 0.82-0.97).

CONCLUSION

A PLASMIC score threshold of ≥5 is associated with high sensitivity and NPV and may be a useful screening tool for identifying patients who are unlikely to have TTP and do not require TPE, though prospective assessment is required. A PLASMIC score <6 appears to have insufficient sensitivity to rule out TTP and the need for TPE.

Low levels of ADAMTS-13 with high anti-ADAMTS-13 antibodies during remission of immune-mediated thrombotic thrombocytopenic purpura highly predict for disease relapse: A multi-institutional study

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a life-threatening immune-mediated thrombotic microangiopathy. Daily therapeutic plasma exchange (TPE) and the optimized use of rituximab have strikingly improved the outcome of this disease, however the rate of disease recurrence remains high. Specific predictors of relapse in patients in remission can be relevant for an optimal patient management. In this study, we aimed to identify predictive variables of disease relapse in a multicenter cohort of 74 out of 153 iTTP patients. They were tested at different time points during remission for the levels of ADAMTS-13 activity and autoantibody, and did not receive pre-emptive treatment for ADAMTS-13 activity deficiency during remission. The results showed that the association of ADAMTS13 activity ≤20% with a high anti-ADAMTS-13 titer at remission, and the time to response to first line treatment ≥13 days, were independent predictive factors of disease relapse. In addition, the use of rituximab in patients with exacerbation or refractoriness to TPE was significantly associated with reduced relapse rate. By Cox regression analysis, patients with ADAMTS-13 activity ≤20% plus anti-ADAMTS13 antibody titer ≥15 U/mL at remission had an increased risk of relapse (HR 1.98, CI 95% 1.087-3.614; P < .02). These findings may help to outline more personalized therapeutic strategies in order to provide faster and sustained responses to first-line iTTP treatment and prevent relapses in these patients.

Does Outcome/Survival of Patients With Myelodysplastic Syndromes Should Be Predicted by Reduced Levels of ADAMTS-13? Results From a Pilot Study

INTRODUCTION

Von Willebrand factor (vWF) cleaving protease ADAMTS-13 has a key role for maintaining normal size of vWF. A deficiency or dysfunction of vWF cleaving protease is associated with ultra large vWF multimers and thrombotic microangiopathy. Patients with cancers have reduced levels of vWF cleaving protease. In this pilot study, we have evaluated whether or not deficiencies of ADAMTS-13 were present in myelodysplastic syndromes (MDS). Moreover, we assessed if a reduction in basal levels of ADAMTS-13 may play a role in the prognosis of MDS.

PATIENTS AND METHODS

We measured and compared the levels of vWF cleaving protease ADAMTS-13 in 100 patients with MDS and 35 healthy controls. Patients were divided into 2 groups according to the International Prognostic Scoring System: group I consisting of 44 patients with low-risk MDS and group II of 56 patients with high-risk MDS. Patients with high-risk and low-risk MDS presented significantly lower levels of ADAMTS-13 than controls (P < .001 and P = .0177, respectively). High-risk patients had significantly lower levels of ADAMTS-13 when compared with the low-risk group (P < .001).

RESULTS

We found that reduced levels of ADAMTS-13 have a relationship with overall survival (P < .001). Statistical analysis showed that ADAMTS-13 correlates with cytogenetics (P < .001) and a tendency of slight correlation with platelet count and basal levels of ADAMTS-13 (R, 0.35; P value, 0.001). Moreover, we found that levels of ADAMTS-13 have correlation with response to treatment (P < .001).

CONCLUSIONS

ADAMTS-13 in MDS might represent a surrogate marker of prognosis, response to therapy, or disease progression. Further studies are needed.

Comparison of low fixed dose versus standard-dose rituximab to treat thrombotic thrombocytopenic purpura in the acute phase and preemptively during remission

The standard dose of rituximab used in B-cell hematological malignancies, 375 mg/m² weekly, may be excessive for autoimmune conditions. Successful use of a low, fixed dose of 100-200 mg of rituximab, weekly for 4 weeks, has been reported in the literature in the treatment of autoimmune thrombotic thrombocytopenic purpura (aTTP). We retrospectively analyzed our rituximab data in aTTP over a 13-year-period for 39 patients, with the aim of comparing response and outcomes with a standard lymphoma-dose course versus a low fixed 100 mg-dose course. Compared to the standard dose (17 patients, 17 courses of 4 infusions), our patients who received a low dose (8 patients, 9 courses of 4 infusions) had a possibly lower baseline risk but did achieve a similar time to remission and number of plasma exchange procedures to remission. Preemptive low-dose courses for ADAMTS13 activity <50 % during remission (6 patients, 10 courses of 4 infusions) achieved a median peak ADAMTS13 activity of 99 %, in a median of 1 month, with no clinical relapses. Our results provide additional evidence for the efficacy of low-dose rituximab, with the benefit of much lower cost, less infusion time, and theoretically lower risk of toxicity.

Real-world data confirm the effectiveness of caplacizumab in acquired thrombotic thrombocytopenic purpura

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare but life-threatening condition. In 2018, the nanobody caplacizumab was approved for the treatment of adults experiencing an acute episode of aTTP, in conjunction with plasma exchange (PEX) and immunosuppression for a minimum of 30 days after stopping daily PEX. We performed a retrospective, observational analysis on the use of caplacizumab in 60 patients from 29 medical centers in Germany during acute disease management. Caplacizumab led to a rapid normalization of the platelet count (median, 3 days; mean 3.78 days). One patient died after late treatment initiation due to aTTP-associated complications. In 2 patients with initial disease presentation and in 4 additional patients with laboratory signs of an exacerbation or relapse after the initial therapy, PEX-free treatment regimens could be established with overall favorable outcome. Caplacizumab is efficacious in the treatment of aTTP independent of timing and ancillary treatment modalities. Based on this real-world experience and published literature, we propose to administer caplacizumab immediately to all patients with an acute episode of aTTP. Treatment decisions regarding the use of PEX should be based on the severity of the clinical presentation and known risk factors. PEX might be dispensable in some patients.

Et Tu, B12? Cobalamin Deficiency Masquerading As Pseudo-Thrombotic Microangiopathy

Vitamin B12 deficiency is classically associated with megaloblastic anemia. Possible cobalamin deficiency is not investigated once hemolysis is seen. Around 2.5% of cases can present as pseudo-thrombotic microangiopathy (TMA). A swift identification of this means the difference between an easy solution and a protracted one for the patient. A 74-year-old man with no past medical history presented with exertional dyspnea, fatigue, and increasing anorexia over two weeks. Physical examination including a neurological examination was normal. Laboratory tests revealed pancytopenia, unconjugated hyperbilirubinemia, elevated LDH (lactate dehydrogenase), low haptoglobin, and fragmented red blood cells (RBCs) on the peripheral smear, but normal FDP (fibrinogen degradation product) and fibrinogen. The absolute reticulocyte count was reduced as opposed to the expected elevation. Vitamin B12 levels were undetectable, and severe cobalamin deficiency from pernicious anemia was found to be the paramount etiology. Cobalamin deficiency causing pseudo-TMA baffles most physicians. Advanced pernicious anemia is thought to cause intramedullary hemolysis, resulting in peripheral pancytopenia. The fragile RBCs are easily sheared, producing schistocytosis without platelet microthrombi. In contrast to hemolytic anemias, reticulocyte count is low given the unavailability of B12 for erythropoiesis. Reticulocytopenia is a universal finding in cases of pseudo-TMA. Around 38.8% of cases with pseudo-TMA are misdiagnosed as thrombotic thrombocytopenic purpura and treated with plasma product therapy. Keeping an eye out for reticulocytopenia in cases of hemolysis could mean a world of difference for the patient.

Novel antiplatelet strategies targeting VWF and GPIb

Von Willebrand factor has a pivotal role in primary hemostasis. Its role in thrombotic microangiopathies (TMA), as well as cardiovascular disease, has been demonstrated. Thrombotic thrombocytopenic purpura (TTP), a thrombotic microangiopathy, is a life-threatening condition with a high mortality rate if untreated. Current management strategies comprise plasma exchange to remove autoantibodies and replenish ADAMTS13, along with immunosuppressive agents in immune TTP. This review focuses on novel antiplatelet strategies that target VWF and GPIb. The benefits of the nanobody caplacizumab in achieving faster normalization of platelet count, as well as reduced thromboembolic events were shown through TITAN and HERCULES trials, and these findings have been practice changing. The use of caplacizumab in patients with immune TTP (iTTP) has now become well established. Potential benefits of ARC1779 and N-acetylcysteine have also been shown on a small scale in iTTP, however these lack evidence through larger randomized controlled trials. Further therapies, some in early phase, others in clinical practice, target platelet aggregation within arteries and their utility is presented with cerebrovascular disorders.

HLA loci predisposing to immune TTP in Japanese: potential role of the shared ADAMTS13 peptide bound to different HLA-DR

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare autoimmune disorder caused by neutralizing anti-ADAMTS13 autoantibodies. In white individuals, HLA allele DRB1*11 is a predisposing factor for iTTP, whereas DRB1*04 is a protective factor. However, the role of HLA in Asians is unclear. In this study, we analyzed 10 HLA loci using next-generation sequencing in 52 Japanese patients with iTTP, and the allele frequency in the iTTP group was compared with that in a Japanese control group. We identified the following HLA alleles as predisposing factors for iTTP in the Japanese population: DRB1*08:03 (odds ratio [OR], 3.06; corrected P [Pc] = .005), DRB3/4/5*blank (OR, 2.3; Pc = .007), DQA1*01:03 (OR, 2.25; Pc = .006), and DQB1*06:01 (OR,: 2.41; Pc = .003). The estimated haplotype consisting of these 4 alleles was significantly more frequent in the iTTP group than in the control group (30.8% vs 6.0%; Pc &lt; .001). DRB1*15:01 and DRB5*01:01 were weak protective factors for iTTP (OR, 0.23; Pc = .076; and OR, 0.23, Pc = .034, respectively). On the other hand, DRB1*11 and DRB1*04 were not associated with iTTP in the Japanese. These findings indicated that predisposing and protective factors for iTTP differ between Japanese and white individuals. HLA-DR molecules encoded by DRB1*08:03 and DRB1*11:01 have different peptide-binding motifs, but interestingly, bound to the shared ADAMTS13 peptide in an in silico prediction model.

Time from suspected thrombotic thrombocytopenic purpura to initiation of plasma exchange and impact on survival: A 10-year provincial retrospective cohort study

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) with significant morbidity and mortality. Guidelines recommend initiating plasma exchange within 4-8 h of suspected diagnosis. It is unclear what are real-world practice patterns and whether delays >8 h increases mortality.

OBJECTIVES

To determine if delayed initiation of plasma exchange is associated with increased risk of death and complications.

METHODS

In this retrospective cohort study, we evaluated the time from suspected diagnosis to plasma exchange in all adults presenting with suspected TTP to apheresis centres in Alberta, Canada (2008-2018). Among patients with acquired TTP, the association between delayed plasma exchange and risk of death was evaluated using Cox regression.

RESULTS

Overall 190 episodes of suspected TTP were included among 163 individuals. Acquired TTP was confirmed in 61 patients. Inappropriate Emergency Department triage occurred in 59%. The median time from suspected diagnosis to first plasma exchange was 10.7 h; 59% had delayed plasma exchange >8 h, among whom plasma infusion was administered in only 45%. 36% of suspected TTP and 13% of confirmed TTP patients died. Delayed plasma exchange between 8 and 24 h was not associated with a significantly higher risk of death (adjusted hazards ratio; aHR 0.63, 95% CI 0.08-4.83) in confirmed TTP. On the other hand, the risks of death (aHR 1.40, 95% CI 0.20-9.79) and major thrombotic events (aHR 2.9, 95% CI 0.6-12.8) were markedly increased with >24 h delay.

CONCLUSIONS

Our study demonstrated that TTP care in a real-world setting is discordant with expert guidelines due to multiple barriers. There is a gradient of increased mortality risk and thrombotic complications with longer treatment delays, although the study is likely underpowered.

Pregnancy and non-pregnancy related immune thrombotic thrombocytopenic purpura in women of reproductive age

Pregnancy is a precipitating factor for immune thrombotic thrombocytopenic purpura (iTTP). We compared the clinical course and outcomes of iTTP in women of reproductive age, between those with pregnancy- and non-pregnancy-related iTTP. A review of all reproductive-aged women diagnosed with iTTP during 2010-2019 in seven university hospitals in Israel. Of 42 cases of iTTP, 12 (28.6%) were pregnancy-related. At presentation, the laboratory profiles did not differ significantly between those with pregnancy- and non-pregnancy-related iTTP, including hemoglobin (median 8.4 vs 8.0 g/dL), platelet count (12.5 vs. 11.5 X 10⁹/L); and levels of bilirubin (1.23 vs. 1.82 mg/dL), lactate dehydrogenase (1615 vs. 1701 U/L), creatinine (0.61 vs. 0.79 mg/dL) and anti-ADAMTS13 antibodies titer (75 vs. 82 U/mL). The proportions of women with renal, neurologic, or hepatic involvement were similar between the groups. Cardiac involvement was more common among those with pregnancy-related disease (25.0% vs. 3.3%, P = 0.06). The median number of courses of plasma-exchange therapy was 11 for both groups. All the women were treated with parenteral corticosteroids and the rate of adjunctive treatments did not differ between the groups (P = 0.30). Four women (one-third) with pregnancy-related disease had preeclampsia. Two women (16.7%) with pregnancy-related iTTP died during the acute episode (P = 0.07); no deaths were observed in the non-pregnancy-related group. Among reproductive-aged women with iTTP, most clinical and laboratory profiles were similar between those with pregnancy- and non-pregnancy-related disease. However, the higher rates of cardiac involvement and mortality among women with pregnancy-related iTTP highlight its challenging management.

Upshaw-Schulman syndrome-associated ADAMTS13 variants possess proteolytic activity at the surface of endothelial cells and in simulated circulation

ADAMTS13 regulates the hemostatic activity of von Willebrand factor (VWF). Determined by static assays, proteolytic activity <10IU/dL in patient plasma, in absence of ADAMTS13 autoantibodies, indicates Upshaw-Schulman syndrome (USS); the congenital form of Thrombotic Thrombocytopenic Purpura (TTP). We have recently functionally characterized sixteen USS-associated ADAMTS13 missense variants under static conditions. Here, we used two assays under shear flow conditions to analyze the activity of those seven mutants with sufficiently high residual secretion plus two newly identified variants. One assay determines cleavage of VWF strings bound to the surface of endothelial cells. The other, light transmission aggregometry-based assay, mimics degradation of VWF-platelet complexes, which are likely to be present in the circulation during TTP bouts. We found that 100 ng/ml of all variants were able to cleave about 80–90% of VWF strings even though 5 out of 9 exhibited activity ≤1% in the state-of-the-art static assay at the same concentration. These data indicate underestimation of ADAMTS13 activity by the used static assay. In simulated circulation, two variants, with missense mutations in the vicinity of the catalytic domain, exhibited only minor residual activity while all other variants were able to effectively break down VWF-platelet complexes. In both assays, significant proteolytic activity could be observed down to 100 ng/ml ADAMTS13. It is thus intriguing to postulate that most variants would have ample activity if secretion of 10% of normal plasma levels could be achieved.

Complementopathies and precision medicine

The renaissance of complement diagnostics and therapeutics has introduced precision medicine into a widened field of complement-mediated diseases. In particular, complement-mediated diseases (or complementopathies) with ongoing or published clinical trials of complement inhibitors include paroxysmal nocturnal hemoglobinuria, cold agglutinin disease, hemolytic uremic syndrome, nephropathies, HELLP syndrome, transplant-associated thrombotic microangiopathy, antiphospholipid antibody syndrome, myasthenia gravis, and neuromyelitis optica. Recognizing that this field is rapidly expanding, we aim to provide a state-of-the-art review of (a) current understanding of complement biology for the clinician, (b) novel insights into complement with potential applicability to clinical practice, (c) complement in disease across various disciplines (hematology, nephrology, obstetrics, transplantation, rheumatology, and neurology), and (d) the potential future of precision medicine. Better understanding of complement diagnostics and therapeutics will not only facilitate physicians treating patients in clinical practice but also provide the basis for future research toward precision medicine in this field.

Expert consensus on the diagnosis and treatment of thrombocytopenia in adult critical care patients in China

Thrombocytopenia is a common complication of critical care patients. The rates of bleeding events and mortality are also significantly increased in critical care patients with thrombocytopenia. Therefore, the Critical Care Medicine Committee of Chinese People's Liberation Army (PLA) worked with Chinese Society of Laboratory Medicine, Chinese Medical Association to develop this consensus to provide guidance for clinical practice. The consensus includes five sections and 27 items: the definition of thrombocytopenia, etiology and pathophysiology, diagnosis and differential diagnosis, treatment and prevention.

Potential impact of a delayed ADAMTS13 result in the treatment of thrombotic microangiopathy: an economic analysis

BACKGROUND

A pre-plasma exchange ADAMTS13 measurement differentiates thrombotic thrombocytopenic purpura (TTP) from other forms of thrombotic microangiopathy (TMA). Given that many hospitals do not perform the ADAMTS13 assay in-house and that the turnaround time (TAT) differs among reference laboratories, we performed an analysis investigating the potential impact of a delay in obtaining the results on the healthcare system.

METHODS

An economic model was developed to estimate the impact of a delay in obtaining the pretreatment ADAMTS13 results on patients admitted with TMA with cost (US dollars) as the primary outcome. Incremental cost-effectiveness ratio (ICER) as a composite outcome was calculated from both cost and life days [LDs], an effectiveness surrogate marker. Model parameters were gathered from the medical literature, except for the institutional cost of the ADAMTS13 test.

RESULTS

In patients with TMA, during the 6-day study period, the incremental cost to the healthcare system ranged from approximately $4155 to $5123 for every 1-day delay in obtaining the pre-exchange ADAMTS13 results with virtually no change in the effectiveness marker. The ICER composite outcome established the cost-effectiveness of having a fast TAT for pre-exchange ADAMTS13 results. Probabilistic sensitivity analyses also confirmed the robustness of the model.

CONCLUSIONS

In patients with clinical presentations of TMAs, having a rapid TAT for pre-exchange ADAMTS13 measurement appeared to be cost-effective. If testing cannot be performed in-house, then our findings support the necessity of contracting with a reference laboratory that can reliably provide the result, preferably within 1 day of admission.

Immune thrombotic thrombocytopenic purpura in older patients: prognosis and long-term survival

Older age is associated with increased mortality in immune thrombotic thrombocytopenic purpura (iTTP). Yet, data are scarce regarding iTTP occurring among older patients. To assess clinical features and long-term impact of iTTP on mortality in older patients (>60 years old), characteristics and prognoses of adult iTTP patients enrolled in the French Reference Center for Thrombotic Microangiopathies registry between 2000 and 2016 were described according to age (<60 years old or ≥60 years old). Long-term mortality of iTTP older survivors was compared with that of non-iTTP geriatric subjects. Comparing, respectively, older iTTP patients (N = 71) with younger patients (N = 340), time from hospital admission to diagnosis was longer (P < .0001); at diagnosis, delirium (P = .034), behavior impairment (P = .045), renal involvement (P < .0001), and elevated troponin level (P = .025) were more important whereas cytopenias were less profound (platelet count, 22 × 103/mm3 [9-57] vs 13 × 103/mm3 [9-21], respectively [P = .002]; hemoglobin level, 9 g/dL [8-11] vs 8 g/dL [7-10], respectively [P = .0007]). Short- and mid-term mortalities were higher (P < .0001) and increased for every 10 years of age range. Age ≥60 years, cardiac involvement, increased plasma creatinine level, and total plasma exchange volume were independently associated with 1-month mortality. Compared with a non-iTTP geriatric population, older survivors showed an increased long-term mortality (hazard ratio = 3.44; P < .001). In conclusion, older iTTP patients have atypical neurological presentation delaying the diagnosis. Age negatively impacts short-term but also long-term mortality.

[Clinical characteristics of 83 patients with thrombotic thrombocytopenic purpura]

Objective: To analyze the clinical characteristics, treatment and prognosis of patients with thrombotic thrombocytopenic purpura (TTP) . Methods: 83 patients with TTP from May 1998 to May 2019 were analyzed retrospectively. Results: Among the 83 patients, there were 27 males and 56 females, with a median age of 39 (10-68) years. 41 cases (49.4%) showed pentalogy syndrome and 79 cases (95.2%) showed triad syndrome. 78.0% (46/59) of the patients had a PLASMIC score of 6 or higher. TTP gene mutations was detected in 5 of 10 patients. The activity of von Willebrand factor-cleaving protease (ADAMTS13) , which was detected in 10 patients before plasma exchange (PEX) , was less than 10% in 9 patients. 83 patients were treated with PEX/plasma infusion and glucocorticoid, 35 of which were treated combined with rituximab and/or immunosuppressant. The median follow-up was 34 (1-167) months, the effective rate was 81.9%, the remission rate was 63.9%, the relapse rate was (35.7 ±7.1) %, and the 3-year overall survival (OS) rate was (78.6 ±4.6) %. The effective rate (72.9%vs 94.3%, P=0.019) and OS rate[ (63.8±7.5) %vs (94.3±3.9) %, χ(2)=8.450, P=0.004] in the group treated with PEX/PI and glucocorticoid alone were lower than those in the group treated combined with rituximab and/or immunosuppressant. COX multivariate analysis showed that age (HR=1.111, 95%CI 1.044-1.184, P=0.001) and alanine transaminase (ALT) /aspartate aminotransferase (AST) (HR=1.353, 95%CI 1.072-1.708, P=0.011) were independent risk factors for OS. Conclusion: Most patients with TTP have triad syndrome, accompanied by a decrease in ADAMTS13 activity. Plasma infusion and glucocorticoid combined with rituximab, immunosuppressive therapy could improve overall survival. The prognosis of patients with older age and high ALT/AST ratio is poor.

Pre-transplant sTIM-3 levels may have a predictive impact on transplant outcome in acute leukemia patients

Objectives: T-cell immunoglobulin and mucin domain-containing protein-3 (TIM-3) is considered as a negative regulator of T-cell driven immune response. This study is planned to investigate the prognostic role of pre-transplant soluble TIM-3 (sTIM-3) levels in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Methods: Pre-transplant serum sTIM-3 levels were measured in 177 allo-HSCT recipients [median age: 36(16-66) years; male/female: 111/66]. Results: Pre-transplant sTIM-3 levels were significantly higher in acute myeloid leukemia (AML) patients compared to acute lymphoblastic leukemia (ALL) patients (p = 0.01). Pre-transplant sTIM-3 levels were significantly lower in patients with abnormal cytogenetics (p = 0.017). Pre-transplant sTIM-3 levels were significantly higher in patients who developed viral hemorrhagic cystitis (p = 0.034). A positive correlation was demonstrated between sTIM-3 levels and acute graft versus host disease (GvHD) grade (p = 0.013; r = 0.299). Overall survival (OS) was not statistically different between low- and high-TIM-3 groups (%35.2 vs %20.4; p > 0.05). Primary diagnosis (p = 0.042), sinusoidal obstruction syndrome (p < 0.001), acute GvHD (p = 0.001), chronic GvHD (p = 0.009) and post-transplant relapse (p = 0.003) represented significant impact on OS. Discussion: Increased sTIM-3 levels in AML patients seem to be compatible with the previous reports. The inhibitor role of TIM-3 in cellular immune response may be a possible explanation for the association of sTIM-3 with viral infections and GvHD. However, the main challenge remains to be the ambiguous association of pre-transplant sTIM-3 levels and post-transplant complications, as allo-HSCT recipients are expected to represent donor genetic features in the post-transplant setting. Conclusion: Further studies are warranted to clarify the particular role of sTIM-3 in the allo-HSCT setting.

Caplacizumab in adult patients with acquired thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is usually a fatal disease caused by a deficiency of the metalloproteinase, ADAMTS13, often due to autoimmunity. This leads to the development of pathogenic multimers of von Willebrand factor (vWF), causing an inappropriate interaction of platelets and vWF. This results in a thrombotic microangiopathy, which is treated with therapeutic plasma exchange and immune suppression. Although this treatment has reduced the mortality of TTP to only about 20%, there have been no recent significant advances in the treatment of TTP. Recently, a novel agent has been approved for use in TTP. Caplacizumab, which binds to the A1 domain of vWF, prevents the adhesion of platelets to vWF. It is a first in-class ‘nanobody’, that in clinical trials has shown marked efficacy in treating TTP and its complications. This review will discuss the development and implications of caplacizumab in the treatment of TTP.

Thrombotic Thrombocytopenic Purpura, Heparin-Induced Thrombocytopenia, and Disseminated Intravascular Coagulation

Hemostatic abnormalities are common among critically ill patients and are associated with a high risk of bleeding. The abnormalities range from isolated thrombocytopenia or prolongation of global coagulation assays to complex disease states, such as thrombotic microangiopathic syndromes, and can be associated with a wide range of conditions, including trauma, surgery, acute disease processes, cardiopulmonary bypass, and exposure to drugs and blood products. Prompt identification of underlying causes is important because treatment strategies vary. Moreover, prompt initiation of both supportive and specific treatments is vital to decrease the morbidity and mortality in the intensive care unit.

Efficacy and safety of open-label caplacizumab in patients with exacerbations of acquired thrombotic thrombocytopenic purpura in the HERCULES study

BACKGROUND

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare, life-threatening autoimmune thrombotic microangiopathy. Caplacizumab, an anti-von Willebrand Factor Nanobody® , is effective for treating aTTP episodes and is well tolerated.

OBJECTIVES AND METHODS

In the phase 3 HERCULES trial (NCT02553317), patients with aTTP received double-blind caplacizumab or placebo during daily therapeutic plasma exchange (TPE) and for ≥30 days thereafter. Patients who experienced an exacerbation while on blinded study drug treatment switched to receive open-label caplacizumab plus re-initiation of daily TPE. Exacerbations were defined as recurrence of disease occurring within 30 days after cessation of daily TPE.

RESULTS

Thirty-one patients (placebo, n = 28; caplacizumab, n = 3) had an exacerbation during double-blind treatment. Twenty-eight patients switched to open-label caplacizumab (placebo, n = 26; caplacizumab, n = 2); the three others discontinued upon exacerbation. Median time to platelet count response (≥150 × 109 /L) was 3.49 days upon receiving caplacizumab. There were no deaths. During open-label treatment, further exacerbation or a major thromboembolic event (vena cava thrombosis) was experienced by one patient (3.6%) each. Consistent with the double-blind phase, the most frequent treatment-emergent adverse events were catheter site hemorrhage (28.6%), headache (21.4%), and epistaxis (17.9%).

CONCLUSIONS

These results suggest that caplacizumab was efficacious and well tolerated in patients with aTTP who experienced a disease exacerbation during double-blind treatment in HERCULES.