Thrombotic and thromboembolic events, with or without thrombocytopenia, following viral vector-based COVID-19 vaccines administration: a systematic review protocol. (preprint)

BackgroundViral vector-based COVID-19 vaccines have proven to be effective and safe in clinical trials and post-authorization studies. Although infrequent, some serious thrombotic and thromboembolic events following immunization have emerged, and causality assessment committees must consider and critically assess different sources of evidence to inform their decisions about whether these events supposedly attributable to vaccination or immunization (ESAVI) are associated with the vaccine or are coincidental. Therefore, this systematic review aims to gather information on the association and biological mechanisms between thrombotic and thromboembolic events, with or without thrombocytopenia, and the administration of viral vector-based COVID-19 vaccines. MethodsWe will conduct a systematic review following the evidence synthesis framework proposed by the Pan American Health Organization to support the ESAVI causality assessment. We will search for primary clinical and preclinical studies in the Epistemonikos COVID-19 L.OVE (Living Overview of the Evidence) repository, a comprehensive and validated source of COVID-19 evidence. We will include studies reporting any thrombotic or thromboembolic event, with or without thrombocytopenia, after the administration of a viral vector-based COVID-19 vaccine. The screening and data extraction will be performed by two independent authors. We will assess the risk of bias by two reviewers using the appropriate tool for each study design. Discrepancies will be discussed or resolved by a third author. We will use GRADE to assess the certainty of evidence for clinical studies and prepare summary of findings tables. For individual-based (case series and case reports) and preclinical studies, we will summarize the results in descriptive tables. Expected results and implicationsThis will be the first systematic review using the evidence synthesis framework for ESAVI causality assessment, currently under validation by the Pan American Health Organization and the Epistemonikos Foundation. By gathering clinical and preclinical evidence, it is expected to inform about the risks of thromboembolic events following vaccination with viral vector-based COVID-19 vaccines, and also the possible underlying biological mechanisms. Policymakers, such as safe vaccination committees, and other evidence synthesis authors could replicate this novel methodology to strengthen the evidence-based ESAVI causality assessment.

Inadvertent Exposure to Pharmacologically Designed Lipid Nanoparticles Via Bodily Fluids: Biologic Plausibility and Potential Consequences (preprint)

Exposure to vaccine lipid nanoparticles, mRNA, adenoviral DNA, and or Spike protein from one of the approved Covid-19 vaccines, or through secondary exposure, as through blood transfusion, is a potential source of harm. Blood reactions are an acknowledged side-effect of Covid-19 vaccination, not limited to hemolysis, paroxysmal nocturnal hemoglobinuria, chronic cold agglutinin disease, immune thrombocytopenia, haemophagocytosis, hemophagocytic lymphohistiocytosis, and many other blood related conditions. The observation of adverse events has motivated investigation into the cardiovascular mechanisms of harm by Covid-19 vaccines, and the biodistribution of vaccine contents. Biodistribution may not be limited to the body of the vaccine recipient, as a growing body of evidence demonstrates the possibility of secondary exposure to vaccine particles. These can be via bodily fluids and include the following routes of exposure: blood transfusion, organ transplantation, breastfeeding, and possibly other means. As covid-19 vaccines are associated with an increased risk of stroke, the persistence of vaccine artifacts in the blood presents a possible threat to a recipient of a blood donation from a vaccinated donor who suffered from vaccine induced thrombosis or thrombocytopenia. (VITT) We assess the feasibility and significance of these risks through an overview of the case report literature of blood disorders in vaccinated individuals, pharmacovigilance reports from the US Vaccine Adverse Events Reporting System (VAERS) and a meta-analysis of the available literature on organ transplants from vaccinated organ donors. Our analysis establishes biological mechanistic plausibility, a coherent safety signal in pharmacovigilance databases for secondary vaccine contents exposure (for the cases of blood transfusion and breastfeeding) and also an elevated level of adverse events in organ transplants from VITT-deceased donors, echoing increases in organ transplantation related complications seen in national statistics for some countries. Secondary exposure to vaccine artifacts is a potential explanation for some of the cases put forth, and requires a deeper investigation.

The Relationship Between COVID-19 Suspected Patient's Coagulation and Platelet Parameters and Polimerase Chain Reaction Results (preprint)

Aim: Our aim was to investigate the relationship between prothrombintime(PT), activated partial thromboplastin time (aPTT), INR (International Normalized Ratio) and D-dimer levels, platelet (PLT)levels at admission to hospital and positivity or negativity of Polymerase Chain Reaction (PCR) result in patients with suspected COVID-19 followed at COVID-19 services. Material and Method: 238 people who applied with suspicion of COVID-19 in March-April-May of 2020 were included in the study. According to COVID-19 results, PCR negative 119 participants and PCR positive 119 patients were included in the study. PT, aPTT, Ddimer, INR and PLT levels were examined. Results: While PCR negative participants had a mean PT value of 11.46±0.86 sec, PCR positive patients had a mean PT value of 12.97±3.65 sec (p<0.001). There was no significant difference in mean aPTT values of PCR positive and negative patients. Whereas INR, D-dimer increased significantly in PCR positive patients. PLT value decreased from mean value of 266.75±71.36*109/L in PCR negative participants to 241.18±96.64*109/L in PCR positive patients (p=0.002). Conclusion: In our study, it was found that in patients who were admitted to Samsun Training and Research Hospital with COVID-19 suspicion and followed up in COVID-19 services, PT, D-dimer, INR, PLT values were important in detecting Coagulopathy and Thrombocytopenia in the group who were PCR positive according to COVID-19 results. Keywords: COVID-19, PT, aPTT, D-dimer, INR, PLT

Unusual presentation of Thrombotic Thrombocytopenic Purpra in a newly diagnosed pediatric patient with Systemic Lupus Erythematosus in the setting of MIS-C (preprint)

The understanding of Coronavirus disease 2019 (COVID-19) immune dysregulation is evolving. Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease with alternations in both innate and adaptive immunity, probably caused by a complex interplay of genetics and environmental exposure with various triggers. A rare hematological complication of SLE as well as recently reported in adult with COVID-19 is thrombotic thrombocytopenic purpura (TTP). We report a pediatric case with features suggestive of multisystem inflammatory syndrome in children (MIS-C) with coronary artery ectasia, TTP, autoimmune hemolytic anemia (AIHA) and thrombocytopenia with new onset SLE as well.

Is there a Relationship between the COVID-19 Vaccine and Epistaxis? (preprint)

Objectives: The aim of this study was to identify if there was a change in the incidence of epistaxis attendances following initiation of the COVID-19 vaccination programme. Design: A retrospective, cohort study. Setting: A large university teaching hospital with an emergency department (ED). Participants: A study group consisting of adults attending the emergency department for epistaxis over a 2-month period in 2021 and a control group consisting of adults attending the emergency for epistaxis over a 2-month period in 2019. Main outcome measures: The comparison of emergency department admission data with vaccination data between the control and study groups. Results: 187 (0.8% of total ED attendances) epistaxis attendances occurred in 2021 compared to 174 (0.6% of total ED attendances) epistaxis attendances in 2019 (p=0.002). No significant differences in platelet count were observed between the vaccinated (250.52 x109/L) and unvaccinated patients (214 x109/L) in the study group (p=0.117). The mean time between vaccination and presentation with epistaxis was 36 days ± 23.5 (n=102). Conclusion: The COVID-19 vaccine may be responsible for an increased proportion of epistaxis attendances to our emergency department. No evidence of thrombocytopenia was observed amongst patients presenting with epistaxis after vaccine administration. The mean time between vaccination and presentation with epistaxis was over five weeks.

The completion rates of radiotherapy or chemoradiotherapy did not change after SARS-CoV-2 Omicron infection (preprint)

Background: The SARS-CoV-2 Omicron pandemic had a global impact on individuals with cancers. This study aimed to investigate the effect of Omicron infection on cancer patients in China. Methods: A retrospective study was conducted, including 347 patients with cancer who received radiotherapy or chemoradiotherapy between July 2022 and March 2023. The patients were divided into three groups: those without SARS-CoV-2 infection during treatment (Non-COVID-19 group), those who began treatment at least 10 days after first testing positive for SARS-CoV-2 (≥10-d COVID-19 group), and those who began treatment less than 10 days after first testing positive for SARS-CoV-2 (<10-d COVID-19 group). The serum levels of SAA, hsCRP, ALT, etc, were used to assess the severity of inflammation, liver damage, and cardiovascular injury. Results: The proportion of moderate and severe infected cases was higher in ≥10-d COVID-19 group compared with <10-d COVID-19 group (p=0.0446). Additionally, the serum levels of SAA, hsCRP, IL-6 and PCT, were significantly higher in ≥10-d COVID-19 group (p<0.05). Serum ALT, LDH and HBDH levels were also elevated in ≥10-d COVID-19 group (p<0.05). However, no significant differences were observed in frequency of neutropenia, thrombocytopenia and completion rates among three groups. Conclusion: Omicron infection leads to inflammation, liver damage and cardiovascular injury in cancer patients. Surprisingly, the duration of delay in radiotherapy or chemoradiotherapy after Omicron infection did not affect completion rates of current therapy, which was not consistent with the recommendations of NCCN guidelines. Moreover, the severity of Omicron infection was worse among cancer patients who received delayed treatment.

MIS-C, inherited metabolic diseases and methylmalonic acidemia: a case report and review of the literature (preprint)

Bacground Methylmalonic acidemia (MMA) secondary to mutase deficiency, mut0, is an inborn error of metabolism causing complete enzyme deficiency. Multisystem Inflammatory Syndrome in Children (MIS-C) is a hyperinflammatory syndrome characterized by fever, inflammation, multiorgan impairment that manifests 14–60 days after the SARS-CoV-2 infection in patients aged < 21 years. Case presentation We describe the clinical case of a 2-year-old child with MMA secondary to mutase deficiency, with the documented homozygous mutation c.2179 C > T of MMUT gene, associated to mut0 phenotype. One month after SARS-CoV-2 infection, he presented fever, rash, significant increase of C-reactive protein (CRP), ferritin, triglycerides, (interleukin) IL-6, PRO-BNP, compatible with the diagnosis of MIS-C. He was treated with intravenous immunoglobulins (2gr/Kg), methylprednisolone (2 mg/Kg/day), with rapid clinical improvement. Ten days later, he showed the worsening of clinical conditions, with the recurrence of fever, vasculitic rash with palmoplantar extension, further increase of ferritin (1033 ug/l), IL-6 (146 pg/ml), PRO-BNP (5117 pg/ml), triglycerides, anemia, thrombocytopenia, metabolic acidosis with hyperlactatemia (180 mg/dl), increased urinary methylmalonic acid (200 mmol/mCreat), multiorgan failure. He was treated with sodium bicarbonate, thiamine, coenzyme Q, vitamin C, methylprednisolone and anakinra (2 mg/Kg/day). Three days after the start of anakinra, he showed a significant improvement of clinical and biochemical parameters and defervescence. 20 days later, a sepsis from Staphylococcus Aureus and Candida Albicans required the interruption of anakinra, with the worsening of the clinical and haematological parameters and the exitus. Conclusions Only a few cases of patients with inherited metabolic diseases (IMD) and MIS-C are described. However, to our knowledge, this is the first case of MIS-C in MMA described. The description of these clinical cases is a precious lesson for pediatricians to manage IMD therapeutic emergencies. Anakinra must be considered as a safe treatment of choice in IMD patients with MIS-C. The use of anakinra in patients with a severe form of MMA is safe and can be employed to treat MIS-C, gaining a substantial clinical and biochemical improvement.

Thrombotic microangiopathy with kidney involvement in a patient with coronavirus disease 2019: A case report and literature review (preprint)

Background and aim: Millions of people worldwide have suffered from coronavirus disease 2019 (COVID-19). COVID-19 can lead to coagulopathy and thrombosis, presenting as pulmonary artery thromboembolism, deep vein thrombosis, and thrombotic microangiopathy (TMA), the latter being a rare finding in affected patients’ kidneys. Prior reports have rarely addressed the pathophysiology, clinical presentations, and therapeutic options in patients with COVID-19-associated TMA. Case presentation: We herein described a case of renal biopsy-proven TMA after COVID-19 in a 36-year-old woman. Initial examination revealed inflammation, acute kidney injury (AKI), anemia, and thrombocytopenia. She was diagnosed with hemolytic uremic syndrome, pulmonary infection, and COVID-19. After treatment, her condition stabilized but remained hemodialysis-dependent after discharge. One week later, she was re-hospitalized, and physical examination showed anemia and bilateral lower extremity edema. Abdominal ultrasound showed increased bilateral kidney echogenicity. Whole-exome sequencing detected an unknown variant of the C3 gene associated with hemolytic uremic syndrome susceptibility type 5/complement C3 deficiency. Kidney biopsy showed renal artery lesions, including small arteriole endothelial swelling, intimal thickening, mucinous degeneration, luminal occlusion, and small arterial wall necrosis. She received plasma exchange and steroids with significant renal function recovery. Conclusion: TMA likely contributed to AKI after COVID-19,thus supporting the notion that TMA plays an important role in the pathogenesis of COVID-19-related kidney injury. When diagnosing and treating COVID-19 patients with abnormal renal function, clinicians should incorporate kidney biopsy and genetic testing for the complement system, identify renal-limited and systemic TMA, and treat accordingly, which can improve patient outcomes.

Eosinophilic Granulomatosis with Polyangiitis after mRNA-1273 SARS-CoV-2 Vaccine (preprint)

During one of the worst global health crises, millions of people were vaccinated against SARS-CoV-2. In rare cases, new onset systemic inflammatory diseases were reported with temporal coincidence to the vaccination. We describe a case of severe Eosinophilic Granulomatosis with Polyangiitis (EGPA) in a young asthmatic woman, occurring after a 2nd dose of mRNA-1273 vaccine. She presented with multisystem EGPA with cardiac and central nervous system involve-ment, complicated by secondary immune thrombocytopenia (ITP). We review the reported cases of EGPA coinciding with SARS-CoV-2 mRNA vaccination. All potentially vaccine-related EGPA cases reported so far occurred within 14 days from immunization. EGPA is very rare with an incidence of 1:1’000’000 inhabitants and the number of reported post-vaccination EGPA cases lies within the expected incidence rate for the period. While we cannot prove a causal relationship between the vaccine and EGPA onset, the temporal relationship with the vaccine immune stimulation is intriguing, in a disease occurring almost always in adults with asthma and/or chronic rhinosinusitis and driven by an aberrant Th2 lym-phocyte activation with hypereosinophilia. Nevertheless, cases of inflammatory diseases emerging in the context of vaccination remain rare and the benefits of preventing severe Covid presentations with SARS-CoV-2 mRNA vaccines remains unquestionable.

SARS-CoV-2 from a hematological perspective / SARS-CoV-2 desde una perspectiva hematológica

La infección viral respiratoria causada por el SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) produce la enfermedad por coronavirus 2019 o COVID-19. Hasta el 20% al 50% de los pacientes hospitalizados con COVID-19 tienen alteraciones de la coagulación (dímero D elevado, tiempo de protrombina prolongado, trombocitopenia y fibrinógeno bajo). Esta condición se caracteriza por eventos trombóticos más que hemorrágicos. De otro lado, se presenta disfunción endotelial, lo cual explica los niveles elevados de trombina, de dímero D y de otros productos de degradación de fibrina, la trombocitopenia y la prolongación de los tiempos de coagulación; estos cambios terminan por originar hipoxia, oclusión microvascular y congestión pulmonar mediada por trombosis [1]. Se ha demostrado que el tratamiento anticoagulante inicial con heparinas de bajo peso molecular reduce la mortalidad un 48% a los 7 días y un 37% a los 28 días, y logra una mejoría significativa del cociente presión arterial de oxígeno/fracción inspirada de O2 (PaO2/FiO2), al mitigar la formación de microtrombos y la coagulopatía pulmonar asociada, disminuyendo además la inflamación [2]. En el artículo titulado "Alteraciones hematológicas como consecuencia de COVID-19 y sus vacunas", se abordan las anormalidades en la coagulación como la trombocitopenia trombótica inmune inducida por las vacunas contra el SARS-CoV-2. Es importante anotar, que hoy en día la comunidad científica está de acuerdo en que sin la vacunación hubiera sido imposible lograr el control actual que se tiene de la pandemia, pero a la vez se debe tener en cuenta que cualquier inmunización tiene también efectos adversos que por lo general son leves, pero que en raras ocasiones se pueden presentar complicaciones de mayor magnitud

Platelet-neutrophil interaction in COVID-19 and vaccine-induced thrombotic thrombocytopenia.

Coronavirus disease 2019 (COVID-19) is known to commonly induce a thrombotic diathesis, particularly in severely affected individuals. So far, this COVID-19-associated coagulopathy (CAC) has been partially explained by hyperactivated platelets as well as by the prothrombotic effects of neutrophil extracellular traps (NETs) released from neutrophils. However, precise insight into the bidirectional relationship between platelets and neutrophils in the pathophysiology of CAC still lags behind. Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare autoimmune disorder caused by auto-antibody formation in response to immunization with adenoviral vector vaccines. VITT is associated with life-threatening thromboembolic events and thus, high fatality rates. Our concept of the thrombophilia observed in VITT is relatively new, hence a better understanding could help in the management of such patients with the potential to also prevent VITT. In this review we aim to summarize the current knowledge on platelet-neutrophil interplay in COVID-19 and VITT.

Immunohistologic Features of Cerebral Venous Thrombosis Due to Vaccine-Induced Immune Thrombotic Thrombocytopenia.

OBJECTIVES: Vaccine-induced immune thrombotic thrombocytopenia (VITT), a recently described entity characterized by thrombosis at unusual locations such as cerebral venous sinus and splanchnic vein, has been rarely described after adenoviral-encoded COVID-19 vaccines. In this study, we report the immunohistological correlates in 3 fatal cases of cerebral venous thrombosis related to VITT analyzed at an academic medical center. METHODS: Detailed neuropathologic studies were performed in 3 cases of cerebral venous thrombosis related to VITT after adenoviral COVID-19 vaccination. RESULTS: Autopsy revealed extensive cerebral vein thrombosis in all 3 cases. Polarized thrombi were observed with a high density of neutrophils in the core and a low density in the tail. Endothelial cells adjacent to the thrombus were largely destroyed. Markers of neutrophil extracellular trap and complement activation were present at the border and within the cerebral vein thrombi. SARS-CoV-2 spike protein was detected within the thrombus and in the adjacent vessel wall. DISCUSSION: Data indicate that neutrophils and complement activation associated with antispike immunity triggered by the vaccine is probably involved in the disease process.

Pathological Effects of SARS-CoV-19 Associated With Hematological Abnormalities (preprint)

The SARS coronavirus 2 (SARS-CoV-2) is the causative agent of the 2019 coronavirus disease (COVID-19) pandemic that has executed 6.9 million people and infected over 765 million. It’s become a major worldwide health alarm and is also known to cause abnormalities in various systems, including the hematologic system. COVID-19 infection primarily affects the lower res-piratory tract and can lead to a cascade of events, including a cytokine storm, intravascular thrombosis, and subsequent complications such as arterial and venous thromboses. COVID-19 can cause thrombocytopenia, lymphopenia, and neutrophilia, which are associated with worse out-comes. Prophylactic anticoagulation is essential to prevent complication and death rate associated with the virus's effect on the coagulation system. It is crucial to recognize these complications early and promptly start therapeutic anticoagulation to improve patient outcomes. While rare, COVID-19-induced disseminated intravascular coagulation exhibits some similarities to DIC induced by sepsis. LDH, D-dimer, ferritin, and CRP biomarker are often increase in serious COVID-19 cases and poor prognosis. Understanding the pathophysiology of the disease and identifying risk factors for adverse outcomes is critical for effective management of COVID-19.

Significance of heparin induced thrombocytopenia (HIT) in COVID-19: a systematic review and meta-analysis.

Heparin-induced thrombocytopenia (HIT) occurs in approximately 3% of patients receiving heparinoids. About 30-75% of patients with type 2 of HIT develop thrombosis as a result of platelet activation. The most important clinical symptom is thrombocytopenia. Patients with severe COVID-19 are among those receiving heparinoids. This meta-analysis performed to picture the current knowledge and results of published studies in this field. Three search engines were searched and 575 papers were found. After evaluation, 37 articles were finally selected of which 13 studies were quantitatively analyzed. The pooled frequency rate of suspected cases with HIT in 13 studies with 11,241 patients was 1.7%. The frequency of HIT was 8.2% in the extracorporeal membrane oxygenation subgroup with 268 patients and 0.8% in the hospitalization subgroup with 10,887 patients. The coincidence of these two conditions may increase the risk of thrombosis. Of the 37 patients with COVID-19 and confirmed HIT, 30 patients (81%) were treated in the intensive care unit or had severe COVID-19. The most commonly used anticoagulants were UFH in 22 cases (59.4%). The median platelet count before treatment was 237 (176-290) x 103/µl and the median nadir platelet count was 52 (31-90.5) x 103/µl.

Whole Blood Procoagulant Platelet Flow Cytometry Protocol for Heparin-Induced Thrombocytopenia (HIT) and Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) Testing.

Heparin-induced thrombocytopenia (HIT) is a well-characterized, iatrogenic complication of heparin anticoagulation with significant morbidity. In contrast, vaccine-induced immune thrombotic thrombocytopenia (VITT) is a recently recognized severe prothrombotic complication of adenoviral vaccines, including the ChAdOx1 nCoV-19 (Vaxzevria, AstraZeneca) and Ad26.COV2.S (Janssen, Johnson & Johnson) vaccines against COVID-19. The diagnosis of HIT and VITT involve laboratory testing for antiplatelet antibodies by immunoassays followed by confirmation by functional assays to detect platelet-activating antibodies. Functional assays are critical to detect pathological antibodies due to the varying sensitivity and specificity of immunoassays. This chapter presents a protocol for a novel whole blood flow cytometry-based assay to detect procoagulant platelets in healthy donor blood in response to plasma from patients suspected of HIT or VITT. A method to identify suitable healthy donors for HIT and VITT testing is also described.

Multiple Electrode Aggregometry (Multiplate): Functional Assay for Vaccine-Induced (Immune) Thrombotic Thrombocytopenia (VITT).

Vaccine-induced immune thrombotic thrombocytopenia (VITT) was first described in 2021 and represents an adverse reaction to adenoviral vector COVID-19 vaccines AstraZeneca ChAdOx1 nCoV-19 (AZD1222) and Johnson & Johnson Ad26.COV2.S vaccine. VITT is a severe immune platelet activation syndrome with an incidence of 1-2 per 100,000 vaccinations. The features of VITT include thrombocytopenia and thrombosis within 4-42 days of first dose of vaccine. Affected individuals develop platelet-activating antibodies against platelet factor 4 (PF4). The International Society on Thrombosis and Haemostasis recommends both an antigen-binding assay (enzyme-linked immunosorbent assay, ELISA) and a functional platelet activation assay for the diagnostic workup of VITT. Here, the application of multiple electrode aggregometry (Multiplate) is presented as a functional assay for VITT.

Serotonin Release Assay: Functional Assay for Heparin- and Vaccine-Induced (Immune) Thrombotic Thrombocytopenia.

The serotonin release assay (SRA) has been the gold-standard assay for detection of heparin-dependent platelet-activating antibodies and integral for the diagnosis for heparin-induced thrombotic thrombocytopenia (HIT). In 2021, a thrombotic thrombocytopenic syndrome was reported after adenoviral vector COVID-19 vaccination. This vaccine-induced thrombotic thrombocytopenic syndrome (VITT) proved to be a severe immune platelet activation syndrome manifested by unusual thrombosis, thrombocytopenia, very elevated plasma D-dimer, and a high mortality even with aggressive therapy (anticoagulation and plasma exchange). While the platelet-activating antibodies in both HIT and VITT are directed toward platelet factor 4 (PF4), important differences have been found. These differences have required modifications to the SRA to improve detection of functional VITT antibodies. Functional platelet activation assays remain essential in the diagnostic workup of HIT and VITT. Here we detail the application of SRA for the assessment of HIT and VITT antibodies.

Heparin-Induced Thrombotic Thrombocytopenia (HITT) and Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT): Similar but Different.

Heparin-induced thrombocytopenia (HIT) represents an autoimmune process whereby antibodies are formed against heparin in complex with platelet factor 4 (PF4) after heparin administration. These antibodies can be detected by a variety of immunological assays, including ELISA (enzyme-linked immunosorbent assay) and by chemiluminescence on the AcuStar instrument. However, pathological HIT antibodies are those that activate platelets in a platelet activation assay and cause thrombosis in vivo. We would tend to call this condition heparin-induced thrombotic thrombocytopenia (HITT), although some workers instead use the truncated abbreviation HIT. Vaccine-induced (immune) thrombotic thrombocytopenia (VITT) instead reflects an autoimmune process whereby antibodies are formed against PF4 after administration of a vaccine, most notably adenovirus-based vaccines directed against COVID-19 (coronavirus disease 2019). Although both VITT and HITT reflect similar pathological processes, they have different origins and are detected in different ways. Most notable is that anti-PF4 antibodies in VITT can only be detected immunologically by ELISA assays, tending to be negative in rapid assays such as that using the AcuStar. Moreover, functional platelet activation assays otherwise used for HITT may need to be modified to detect platelet activation in VITT.

Knowledge mapping of immune thrombocytopenia: a bibliometric study.

Background: Immune thrombocytopenia (ITP) is an autoimmune disease characterized by isolated thrombocytopenia. Recently, the pathophysiology and novel drugs of ITP have been the focus of researchers with plenty of publications emerging. Bibliometrics is the process of extracting measurable data through statistical analysis of published research studies to provide an insight into the trends and hotspots. Objective: This study aimed to provide an insight into developing trends and hotspots in the field of ITP by bibliometric analysis. Methods: By using three bibliometric mapping tools (bibliometrix R package, VOSviewer, CiteSpace), we summarized the overview information of retrieved publications, as well as the analysis of keyword co-occurrence and reference co-citation. Results: A total of 3299 publications with 78066 citations on ITP research were included in the analysis. The keyword co-occurrence network identified 4 clusters relating to the diagnosis, pathophysiology, and treatment of ITP respectively. Then the reference co-citation analysis produced 12 clusters with a well-structured and highly credible clustering model, and they can be divided into 5 trends: second-line treatment, chronic ITP, novel therapy and pathogenesis, COVID-19 vaccine. Treg cells, spleen tyrosine kinase, and mesenchymal stem cells were the latest hotspots with strong burstness. Conclusion: This bibliometric analysis provided a comprehensive insight into research hotspots and trends on ITP, which would enrich the review of the ITP research.