Advantages and limits of ADAMTS13 testing in thrombotic thrombocytopenic purpura

von Willebrand factor, ADAMTS-13, and thrombospondin 1 in relation to clinical outcomes in elderly patients with a recent myocardial infarction

Background

von Willebrand factor (VWF) multimers are cleaved by A disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13 (ADAMTS-13) into less active fragments. Thrombospondin 1 (TSP-1) competes with VWF's cleavage site, protecting it from degradation. Low ADAMTS-13 and high VWF have been associated with cardiovascular disease and atrial fibrillation (AF).

Objectives

We aimed to investigate whether VWF, ADAMTS-13, and TSP-1 are associated with clinical outcome.

Methods

Elderly patients with a recent myocardial infarction (MI) (n = 1027) were followed for 2 years. Blood was collected 2 to 8 weeks after the MI for ADAMTS-13, VWF, and TSP-1 measures. The primary endpoints (major adverse cardiovascular events; n = 210) included the first event of MI, stroke, heart failure hospitalization, coronary revascularization, and all-cause death. Total mortality was also registered (n = 56). The secondary endpoint was new-onset AF (n = 43).

Results

Concentrations of VWF, ADAMTS-13, and TSP-1 did not intercorrelate. The risk of major adverse cardiovascular events was altered in patients with VWF ≥ median (hazard ratio [HR], 1.4; 95% CI, 1.0-1.8; P = .03) and ADAMTS-13 ≥ median (HR, 0.7; 95% CI, 0.5-0.9; P = .02); however, it was not significant in adjusted models. VWF and ADAMTS-13 were significantly associated with total mortality, with a HR of 2.7 (95% CI, 1.6-4.6; P < .001) for VWF (Q4 vs. Q1-Q3) and HR of 0.3 (95% CI, 0.2-0.5; P < .001) for ADAMTS-13 (Q2-4 vs. Q1). The associations persisted in multivariable analysis, but the significance disappeared for VWF after correcting for high-sensitivity C-reactive protein. The risk of new-onset AF was lower in patients with VWF ≥ median (HR, 0.5; 95% CI, 0.3-1.0; P = .04]), and this was still significant after adjustments.

Conclusion

Although low ADAMTS-13 predicted death, the cardiovascular risk associated with VWF and ADAMTS-13 was weaker than previously reported. Low VWF is associated with new-onset AF and needs further research.

A Case of Thrombotic Thrombocytopenic Purpura Possibly Induced by Graves' Disease

Thrombotic thrombocytopenic purpura (TTP) has historically been diagnosed with a pentad of features, i.e., thrombocytopenia, micro-angiopathic hemolytic anemia (MAHA), fever, neurological abnormalities, and kidney failure. Traditionally, TTP cases have been described in healthy adults. However, their association with autoimmune diseases is now well documented in the literature. There is limited availability of literature on the association between TTP and Graves' disease (GD). Here, we report a case of an adult female, a known case of Graves' disease, who has now been diagnosed with an acquired case of TTP. The presence of MAHA associated with thrombocytopenia was considered a clinical diagnosis of TTP and the patient immediately underwent plasma exchange (PEX), which led to the resolution of complaints. Hyperthyroidism cases should be adequately followed up as clinical severity could lead to the emergence of TTP.

An Imperfect Marker: SLE and TTP-Like MAHA Without Low ADAMTS13

Thrombotic thrombocytopenic purpura (TTP) is a potentially fatal condition that can be challenging for clinicians to identify in the setting of autoimmune diseases such as systemic lupus erythematosus (SLE). This difficulty is compounded when a patient presents with all of the clinical signs of a TTP-like microangiopathy, however, with near normal ADAMTS13. This case report describes a 44-year-old female with a history of SLE who was hospitalized with acute on chronic anemia, thrombocytopenia, and altered mental status. The patient's ADAMTS13 was mildly low; hence, she was initially treated for SLE-associated immune thrombocytopenic purpura without any clinical response. The patient then underwent plasmapheresis (plasma exchange [PLEX]) for treatment of a suspected TTP-like microangiopathy. She responded to PLEX with improvement in her platelet count and mental status. This case illustrates the importance of considering TTP-like microangiopathic hemolytic anemia in the differential for patients with a history of SLE presenting with clinical signs of TTP even in the setting of near-normal ADAMTS13, thus warranting prompt treatment with PLEX.

COVID-19, septic shock and syndrome of disseminated intravascular coagulation syndrome. Part 1

The pandemic of a new coronavirus infection (Coronavirus Disease 2019, COVID-19) caused by SARS-CoV-2 became a real challenge to humanity and the medical community in 2020 and raised a number of medical, social and even philosophical questions. An almost avalanche-like increase in the number of infected people in a short time, due to the high contagiousness of viral infection, allowed us to identify groups of patients with mild, moderate and severe forms of the disease. Doctors around the world are faced with an acute problem of treating a large number of patients in critical conditions caused by COVID-19. From the currently available information on clinical cases of COVID-19, it follows that COVID-19 patients in critical condition have a clinical picture of disseminated intravascular coagulation (DIC), septic shock with the development of multiple organ failure. The first part of the article discusses the pathogenesis of non-specific universal biological responses of the body in critical condition - from the Sanarelli-Schwartzman phenomenon to the DIC, septic shock, systemic inflammatory response syndrome and the so-called neutrophil extracellular traps (NETs). The questions of cytokine storm in severe forms of systemic inflammatory response syndrome (SIRS), the role of inflammation in the activation of coagulation, and the relationship between inflammation and thrombosis are discussed. Modern ideas about the mechanisms of so-called NETosis, their role in the occurrence of immunothrombosis and inflammation-induced thrombosis in autoimmune diseases - vasculitis, antiphospholipid syndrome, and systemic lupus erythematosus is highlighted. The article discusses the possibility of participation of ADAMTS-13 metalloproteinase in the pathogenesis of multiple organ failure in severe endotheliopathy in patients with viral septic shock.

Utilizing a PLASMIC score-based approach in the management of suspected immune thrombotic thrombocytopenic purpura: a cost minimization analysis within the Harvard TMA Research Collaborative

The PLASMIC score is a recently described clinical scoring algorithm that rapidly assesses the probability of severe ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency among patients presenting with microangiopathic haemolytic anaemia. Using a large multi-institutional cohort, we explored whether an approach utilizing the PLASMIC score to risk-stratify patients with suspected immune thrombotic thrombocytopenic purpura (iTTP) could lead to significant cost savings. Our consortium consists of institutions with an unrestricted approach to ADAMTS13 testing (Group A) and those that require pre-approval by the transfusion medicine service (Group B). Institutions in Group A tested more patients than those in Group B (P < 0·001) but did not identify more cases of iTTP (P = 0·29) or have lower iTTP-related mortality (P = 0·84). Decision tree cost analysis showed that applying a PLASMIC score-based strategy to screen patients for ADAMTS13 testing in Group A would have reduced costs by approximately 27% over the 12-year period of our study compared to the current approach. Savings were primarily driven by a reduction in unnecessary therapeutic plasma exchanges, but lower utilization of ADAMTS13 testing and subspecialty consultations also contributed. Our data indicate that using the PLASMIC score to guide ADAMTS13 testing and the management of patients with suspected iTTP could be associated with significant cost savings.

Gemcitabine-induced haemolytic uraemic syndrome in pancreatic adenocarcinoma

A woman in her mid-70s with metastatic pancreatic adenocarcinoma presented with fatigue, nausea and bilateral leg swelling, 4 days after an intravenous gemcitabine infusion. Additional examination and laboratory tests showed mild hypertension, low haemoglobin, high lactate dehydrogenase, low platelet count and high serum creatinine. The patient was subsequently diagnosed with haemolytic uraemic syndrome (HUS), and gemcitabine administration was immediately ceased. The patient received a 5-day course of methylprednisolone, with a full recovery being made 10 days after diagnosis. Clinicians should be aware of the rare but serious complication of gemcitabine-induced HUS (GiHUS), as early diagnosis and management, which includes prompt discontinuation of gemcitabine, are crucial in promptly resolving this condition. This case report describes one treatment that can be used for the treatment of GiHUS, while briefly covering some other novel treatments that have been described in other studies.

Thrombotic thrombocytopenic purpura possibly triggered by Graves' disease

Thrombotic thrombocytopenic purpura (TTP) is a part of a spectrum of thrombotic microangiopathy syndromes which are mainly characterized by platelet aggregation causing microangiopathic hemolytic anemia, thrombocytopenia and microvascular occlusion. In literature, very few cases expressing a direct association between pre-existing Grave’s disease and TTP have been described. A 37-year-old African–American woman with past medical history of Grave’s disease and polysubstance abuse who presented with complaints of dyspnoea at rest and chest pain was diagnosed to have TTP on further evaluation. Patient also showed severely elevated thyroid hormones and suppressed thyroid stimulating hormone levels indicating severe thyrotoxicosis. Initiation of prompt management of TTP and thyrotoxicosis led to a favorable patient outcome. In conclusion, patients presenting with thyrotoxicosis, thrombocytopenia and microangioapthic hemolytic anemia without an alternative cause should be treated and screened for TTP due to the high fatality associated with untreated or untimely detection of this disease.

Thrombotic Thrombocytopenic Purpura in Black People: Impact of Ethnicity on Survival and Genetic Risk Factors

Black people are at increased risk of thrombotic thrombocytopenic purpura (TTP). Whether clinical presentation of TTP in Black patients has specific features is unknown. We assessed here differences in TTP presentation and outcome between Black and White patients. Clinical presentation was comparable between both ethnic groups. However, prognosis differed with a lower death rate in Black patients than in White patients (2.7% versus 11.6%, respectively, P = .04). Ethnicity, increasing age and neurologic involvement were retained as risk factors for death in a multivariable model (P < .05 all). Sixty-day overall survival estimated by the Kaplan-Meier curves and compared with the Log-Rank test confirmed that Black patients had a better survival than White patients (P = .03). Salvage therapies were similarly performed between both groups, suggesting that disease severity was comparable. The comparison of HLA-DRB1*11, -DRB1*04 and -DQB1*03 allele frequencies between Black patients and healthy Black individuals revealed no significant difference. However, the protective allele against TTP, HLA-DRB1*04, was dramatically decreased in Black individuals in comparison with White individuals. Black people with TTP may have a better survival than White patients despite a comparable disease severity. A low natural frequency of HLA-DRB1*04 in Black ethnicity may account for the greater risk of TTP in this population.

Thrombotic microangiopathies

Thrombotic microangiopathy results from thrombotic occlusion of the microvasculature leading to fragmentation of red blood cells, profound thrombocytopenia, and a microangiopathic hemolytic anemia with elevation of lactate dehydrogenase and negative direct Coomb's test. This constellation of clinical and laboratory findings is not due to one disease entity; rather, it represents a variety of underlying diagnoses. Among the major disease entities are TTP/HUS, which can be congenital or acquired, bacterial infections, medications, vascular or endothelial pathology like Kasabach-Merritt phenomenon, and stem cell transplantation. In this paper, we offer a review of some of the major causes of thrombotic microangiopathy.

G, Shapiro A, Okunji C, Kosti I, Shomron N, Grigoryan V, Przytycka TM, Sauna ZE, Salari R, Mandel-Gutfreund Y, Komar AA, Kimchi-Sarfaty C. Characterization of coding synonymous and non-synonymous variants in ADAMTS13 using ex vivo and in silico approaches

Synonymous variations, which are defined as codon substitutions that do not change the encoded amino acid, were previously thought to have no effect on the properties of the synthesized protein(s). However, mounting evidence shows that these “silent” variations can have a significant impact on protein expression and function and should no longer be considered “silent”. Here, the effects of six synonymous and six non-synonymous variations, previously found in the gene of ADAMTS13, the von Willebrand Factor (VWF) cleaving hemostatic protease, have been investigated using a variety of approaches. The ADAMTS13 mRNA and protein expression levels, as well as the conformation and activity of the variants have been compared to that of wild-type ADAMTS13. Interestingly, not only the non-synonymous variants but also the synonymous variants have been found to change the protein expression levels, conformation and function. Bioinformatic analysis of ADAMTS13 mRNA structure, amino acid conservation and codon usage allowed us to establish correlations between mRNA stability, RSCU, and intracellular protein expression. This study demonstrates that variants and more specifically, synonymous variants can have a substantial and definite effect on ADAMTS13 function and that bioinformatic analysis may allow development of predictive tools to identify variants that will have significant effects on the encoded protein.

Development and validation of a predictive model for death in acquired severe ADAMTS13 deficiency-associated idiopathic thrombotic thrombocytopenic purpura: the French TMA Reference Center experience

BACKGROUND

Acquired thrombotic thrombocytopenic purpura is still associated with a 10-20% death rate. It has still not been possible to clearly identify early prognostic factors of death. This study involved thrombotic thrombocytopenic purpura patients with acquired severe (<10% of normal activity) ADAMTS13 deficiency and aimed to identify prognostic factors associated with 30-day death.

DESIGN AND METHODS

The study involved a prospective cohort of patients and was carried out between October 2000 and August 2010. A validation cohort of patients was set up from September 2010 to August 2011. Altogether, 281 (analysis cohort) and 66 (validation cohort) consecutive adult thrombotic thrombocytopenic purpura patients with acquired severe ADAMTS13 deficiency were enrolled. The study evaluated 30-day mortality after treatment initiation according to characteristics at inclusion.

RESULTS

Non-survivors (11%) were older (P=10(-6)) and more frequently presented arterial hypertension (P=5.10(-4)) and ischemic heart disease (P=0.013). Prognosis was increasingly poor with age (P=0.004). On presentation, cerebral manifestations were more frequent in non-survivors (P=0.018) and serum creatinine level was higher (P=0.008). The most significant independent variables determining death were age, severe cerebral involvement and LDH level 10 N or over. A 3-level risk score for early death was defined and confirmed in the validation cohort using these variables, with higher values corresponding to increased risk of early death.

CONCLUSIONS

A risk score for early death was defined in patients with thrombotic thrombocytopenic purpura and validated on an independent cohort. This score should help to stratify early treatment and identify patients with a worse prognosis.

Predictive features of severe acquired ADAMTS13 deficiency in idiopathic thrombotic microangiopathies: the French TMA reference center experience

Severe ADAMTS13 deficiency occurs in 13% to 75% of thrombotic microangiopathies (TMA). In this context, the early identification of a severe, antibody-mediated, ADAMTS13 deficiency may allow to start targeted therapies such as B-lymphocytes-depleting monoclonal antibodies. To date, assays exploring ADAMTS13 activity require skill and are limited to only some specialized reference laboratories, given the very low incidence of the disease. To identify clinical features which may allow to predict rapidly an acquired ADAMTS13 deficiency, we performed a cross-sectional analysis of our national registry from 2000 to 2007. The clinical presentation of 160 patients with TMA and acquired ADAMTS13 deficiency was compared with that of 54 patients with detectable ADAMTS13 activity. ADAMTS13 deficiency was associated with more relapses during treatment and with a good renal prognosis. Patients with acquired ADAMTS13 deficiency had platelet count <30×10⁹/L (adjusted odds ratio [OR] 9.1, 95% confidence interval [CI] 3.4–24.2, P<.001), serum creatinine level ≤200 µmol/L (OR 23.4, 95% CI 8.8–62.5, P<.001), and detectable antinuclear antibodies (OR 2.8, 95% CI 1.0–8.0, P<.05). When at least 1 criteria was met, patients with a severe acquired ADAMTS13 deficiency were identified with positive predictive value of 85%, negative predictive value of 93.3%, sensitivity of 98.8%, and specificity of 48.1%. Our criteria should be useful to identify rapidly newly diagnosed patients with an acquired ADAMTS13 deficiency to better tailor treatment for different pathophysiological groups.