Review and evolution of guidelines for diagnosis of COVID-19 vaccine induced thrombotic thrombocytopenia (VITT)

D-dimer diagnostics: can I use any D-dimer assay? Bridging the knowledge-to-action gap

A State of the Art lecture titled "D-dimer Diagnostics: Can I use any D-dimer assay? Bridging the Knowledge-to-Action gap" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023, included in the session on the clinical impact of variability in commonly used coagulation assays. Here, we review the role of D-dimer, primarily in the outpatient diagnosis of patients with venous thromboembolism (VTE) when combined with clinical decision rules. We focus on the recent large management trials that have studied adjustments of VTE exclusion thresholds for D-dimer based on either prior clinical probability of VTE or patient age, and the resultant benefit of reduced imaging for VTE and improved diagnostic efficiency. In this context, we report on the significant variability between D-dimer results and the multiple D-dimer assays in use worldwide using data from international external quality assurance programs. This variability is particularly high at typical VTE exclusion thresholds. We discuss the potential clinical impact of D-dimer assay substitution on accuracy of diagnosis and risk stratification of patients with VTE. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress and outline future priorities urgently needed to harmonize D-dimer results and reporting that will require international collaboration among multiple stakeholders with an overall goal to close this knowledge-to-action gap.

COVID-19 vaccine-induced immune thrombotic thrombocytopenia: a review

Rare but serious thrombotic incidents in relation to thrombocytopenia, termed vaccine-induced immune thrombotic thrombocytopenia (VITT), have been observed since the vaccine rollout, particularly among replication-defective adenoviral vector-based severe acute respiratory syndrome coronavirus 2 vaccine recipients. Herein, we comprehensively reviewed and summarized reported studies of VITT following the coronavirus disease 2019 (COVID-19) vaccination to determine its prevalence, clinical characteristics, as well as its management. A literature search up to October 1, 2021 using PubMed and SCOPUS identified a combined total of 720 articles. Following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guideline, after screening the titles and abstracts based on the eligibility criteria, the remaining 47 full-text articles were assessed for eligibility and 29 studies were included. Findings revealed that VITT cases are strongly related to viral vector-based vaccines, which are the AstraZeneca COVID-19 vaccine (95%) and the Janssen COVID-19 vaccine (4%), with much rarer reports involving messenger RNA-based vaccines such as the Moderna COVID-19 vaccine (0.2%) and the Pfizer COVID-19 vaccine (0.2%). The most severe manifestation of VITT is cerebral venous sinus thrombosis with 317 cases (70.4%) and the earliest primary symptom in the majority of cases is headache. Intravenous immunoglobulin and non-heparin anticoagulant are the main therapeutic options for managing immune responses and thrombosis, respectively. As there is emerging knowledge on and refinement of the published guidelines regarding VITT, this review may assist the medical communities in early VITT recognition, understanding the clinical presentations, diagnostic criteria as well as its management, offering a window of opportunity to VITT patients. Further larger sample size trials could further elucidate the link and safety profile.

Inferior vena cava and renal vein thrombosis: a rare cause of acute kidney injury in tuberculosis

Recent studies show active tuberculosis induces a prothrombotic state and increases the risk of venous thromboembolism. We report a recently diagnosed case of tuberculosis who presented to our hospital with painful bilateral lower limb swelling and several episodes of vomiting with abdominal pain for 2 weeks. Investigations by a hospital elsewhere 2 weeks ago showed abnormal renal function, misdiagnosed as antitubercular therapy-induced acute kidney injury. D-dimer levels were increased on admission with us, with still deranged renal function. Imaging revealed thrombus at the origin of left renal vein, inferior vena cava and bilateral lower limbs. We started treatment with anticoagulants, which gradually improved kidney function. This case highlights that early diagnosis of renal vein thrombosis and prompt treatment are associated with good clinical outcomes. It also highlights the importance of further studies for risk assessment, prevention strategies and reduction of the burden of venous thromboembolism in patients with tuberculosis.

Platelet Activation and Cytokine Release of Interleukin-8 and Interferon-Gamma-Induced Protein 10 after ChAdOx1 nCoV-19 Coronavirus Vaccine Injection

Coronavirus disease 2019 (COVID-19) vaccines are associated with serious thromboembolic or thrombocytopenic events including vaccine-induced immune thrombocytopenia and thrombosis and immune thrombocytopenia, particularly AZD1222/ChAdOx1. According to the proposed mechanism, COVID-19 vaccines stimulate inflammation and platelet activation. In this study, we analyzed the role of AZD1222/ChAdOx1 vaccines in the activation of platelets and the release of anti-PF4 antibodies and inflammatory cytokines in a cohort of healthy donors without vaccine-induced immune thrombotic thrombocytopenia (VITT). Forty-eight healthy volunteers were enrolled in this study. Blood samples were collected from peripheral blood at three time points: before vaccination and 1 and 7 days after vaccination. Compared with the prevaccination data, a decrease in the leukocyte and platelet counts was observed 1 day after vaccination, which recovered 7 days after injection. The percentage of activated GPIIb/IIIa complex (PAC-1) under high ADP or thrombin receptor-activating peptide stimulation increased 1 day after vaccination. Furthermore, interluekin-8 (IL-8) and interferon-gamma-induced protein 10 (IP-10) increased significantly. Additionally, platelet activation and inflammation, with the release of cytokines, were observed; however, none of the individuals developed VITT. Mild thrombocytopenia with platelet activation and inflammation with an elevation of IL-8 and IP-10 were observed after AZ vaccination.

COVID-19 Vaccine-Associated Immune Thrombosis and Thrombocytopenia (VITT): Diagnostic Discrepancies and Global Implications

Vaccine-induced immune thrombotic thrombocytopenia (VITT) has been reported in association with the coronavirus disease 2019 preventative adenovirus vector-based vaccines ChAdOx1 nCoV-19 (Oxford/AstraZeneca) and Ad26.COV2.S (Janssen/Johnson & Johnson) in hundreds of recipients across the globe. VITT is characterized by thrombosis, typically at unusual sites, low fibrinogen, and elevated plasma D-dimer, generally manifesting between 4 and 28 days following vaccination. Detection of anti-platelet factor antibodies using an enzyme-linked immunosorbent assay (ELISA) is often confirmatory. Although several similar principles subside in most diagnostic criteria for VITT, the presentation of a positive ELISA assay, use of expert hematology and neurology opinion, and exclusion of possible VITT cases outside the "standard" 4 to 28-day timeframe have contributed a lack of global standardization for defining VITT. Accordingly, the global and regional incidence of VITT differs according to the diagnostic pathway and case definition used. This has influenced the public perception of VITT's severity and the decision to use adenovirus vector-based vaccines for limiting severe acute respiratory syndrome coronavirus 2 infection. We hereby delineate the recognized pathogenic mechanisms, global incidence, discrepancies in diagnostic criteria, recommended treatments, and global implications to vaccine hesitancy from this coagulopathy.

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.

Assessment of immunological anti-platelet factor 4 antibodies for vaccine-induced thrombotic thrombocytopenia (VITT) in a large Australian cohort: A multicenter study comprising 1284 patients

BACKGROUND

Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare complication of adenovirus-based vaccines aimed to prevent and minimize COVID-19 and related pathophysiology.

OBJECTIVES

To describe patterns of testing for anti-platelet factor 4 (PF4) antibodies using various ELISA assays in a large Australian cohort and comparative functional platelet activation assays in a subset.

PATIENTS/METHODS

Asserachrom HPIA IgG ELISA was performed in 1284 patients over a period of 12 months, supplemented in select cohorts by comparative ELISA using three other methods (n = 78-179), three different functional assays (flow cytometry, serotonin release assay, and/or Multiplate; n = 476), and rapid immunological chemiluminescence anti-PF4 assay (n = 460), in a multicenter study.

RESULTS

For first episode presentations, 190/1284 (14.8%) ELISA tests were positive. Conversely, most (445/460; 96.7%) chemiluminescence anti-PF4 test results were negative. All functional assays showed associations of higher median ELISA optical density with functional positivity and with high rates of ELISA positivity (64.0% to 85.2%). Data also identified functional positivity in 14.8%-36.0% of ELISA negative samples, suggesting false negative VITT by HPIA IgG ELISA in upward of one third of assessable cases.

CONCLUSION

To our knowledge, this is the largest multicenter evaluation of anti-PF4 testing for investigation of VITT. Discrepancies in test results (ELISA vs. ELISA or ELISA vs. functional assay) in some patients highlighted limitations in relying on single methods (ELISA and functional) for PF4 antibody detection in VITT, and also highlights the variability in phenotypic test presentation and pathomechanism of VITT.

Autoimmune Diseases Affecting Hemostasis: A Narrative Review

Hemostasis reflects a homeostatic mechanism that aims to balance out pro-coagulant and anti-coagulant forces to maintain blood flow within the circulation. Simplistically, a relative excess of procoagulant forces can lead to thrombosis, and a relative excess of anticoagulant forces can lead to bleeding. There are a wide variety of congenital disorders associated with bleeding or thrombosis. In addition, there exist a vast array of autoimmune diseases that can also lead to either bleeding or thrombosis. For example, autoantibodies generated against clotting factors can lead to bleeding, of which acquired hemophilia A is the most common. As another example, autoimmune-mediated antibodies against phospholipids can generate a prothrombotic milieu in a condition known as antiphospholipid (antibody) syndrome (APS). Moreover, there exist various autoimmunity promoting environments that can lead to a variety of antibodies that affect hemostasis. Coronavirus disease 2019 (COVID-19) represents perhaps the contemporary example of such a state, with potential development of a kaleidoscope of such antibodies that primarily drive thrombosis, but may also lead to bleeding on rarer occasions. We provide here a narrative review to discuss the interaction between various autoimmune diseases and hemostasis.

Case report: Vaccine-induced immune thrombotic thrombocytopenia complicated by acute cerebral venous thrombosis and hemorrhage after AstraZeneca vaccines followed by Moderna COVID-19 vaccine booster and surgery

Vaccine-induced thrombotic thrombocytopenia (VITT) is a well-known complication of adenoviral vector COVID-19 vaccines including ChAdOx1 nCoV-19 (AstraZeneca) and Ad26. COV2.S (Janssen, Johnson & Johnson). To date, only a few cases of mRNA COVID-19 vaccine such as mRNA-1273 (Moderna) or BNT162b2 (Pfizer-BioNTech)-induced VITT have been reported. We report a case of VITT with acute cerebral venous thrombosis and hemorrhage after a booster of mRNA-1273 (Moderna) vaccine in a patient previously vaccinated with two doses of the AstraZeneca vaccine. A 42-year-old woman presented with sudden onset of weakness of the right upper limb with focal seizure. She had received two doses of AstraZeneca vaccines and a booster with Moderna vaccine 32 days before presentation. She had also undergone a laparoscopic myomectomy 12 days previously. Laboratory examinations revealed anemia (9.5 g/dl), thrombocytopenia (31 × 10³/μl), and markedly elevated d-dimer (>20.0 mg/L; reference value < 0.5 mg/L). The initial brain computed tomography (CT) was normal, but a repeated scan 10 h later revealed hemorrhage at the left cerebrum. Before the results of the blood smear were received, on suspicion of thrombotic microangiopathy with thrombocytopenia and thrombosis, plasmapheresis and pulse steroid therapy were initiated, followed by intravenous immunoglobulin (1 g/kg/day for two consecutive days) due to refractory thrombocytopenia. VITT was confirmed by positive anti-PF4 antibody and both heparin-induced and PF4-induced platelet activation testing. Clinicians should be aware that mRNA-1273 Moderna, an mRNA-based vaccine, may be associated with VITT with catastrophic complications. Additionally, prior exposure to the AstraZeneca vaccine and surgical procedure could also have precipitated or aggravated autoimmune heparin-induced thrombocytopenia/VITT-like presentation.

Adenovirus-Based Vaccines and Thrombosis in Pregnancy: A Systematic Review and Meta-analysis

BACKGROUND

Rare cases of thrombosis and thrombocytopenia (thrombosis with thrombocytopenia syndrome [TTS]) have been associated with 2 coronavirus disease 2019 adenovirus vector vaccines: the ChAdOx1 nCoV-19 Vaxzevria vaccine (Oxford/AstraZeneca) and the JNJ-7836735 Johnson & Johnson vaccine (Janssen). It is unknown if TTS is a class-mediated effect of adenovirus-based vaccines or if it could worsen known hypercoagulable states. Since most cases of TTS happen in women of childbearing age, pregnancy is a crucial risk factor to assess. Understanding these risks is important for advising vaccine recipients and future adenovirus vector vaccine development.

METHODS

To explore the potential associations of adenovirus-based vaccine components with symptoms of TTS in the general clinical trial population and in pregnant women in clinical trials, we conducted a systematic review and meta-analysis of adenovirus-based vector vaccines to document cases of thrombocytopenia, coagulopathy, and or pregnancy from 1 January 1966 to 9 August 2021.

RESULTS

We found 167 articles from 159 studies of adenovirus vector-based vaccines, 123 of which targeted infectious diseases. In the general population, 20 studies reported an event of thrombocytopenia and 20 studies indicated some coagulopathy. Among pregnant women, of the 28 studies that reported a total of 1731 pregnant women, thrombocytopenia or coagulopathy were not reported.

CONCLUSIONS

In this systematic review and meta-analysis, there was no class-wide effect of adenovirus vector vaccines toward thrombocytopenia or coagulopathy events in the general population or in pregnant women.

Safety of COVID-19 Vaccines: Spotlight on Neurological Complications

The COVID-19 pandemic has led to unprecedented demand on the global healthcare system. Remarkably, at the end of 2021, COVID-19 vaccines received approvals for human use in several countries worldwide. Since then, a solid base for response in the fight against the virus has been placed. COVID-19 vaccines have been shown to be safe and effective drugs. Nevertheless, all kinds of vaccines may be associated with the possible appearance of neurological complications, and COVID-19 vaccines are not free from neurological side effects. Neurological complications of COVID-19 vaccination are usually mild, short-duration, and self-limiting. However, severe and unexpected post-vaccination complications are rare but possible events. They include the Guillain-Barré syndrome, facial palsy, other neuropathies, encephalitis, meningitis, myelitis, autoimmune disorders, and cerebrovascular events. The fear of severe or fatal neurological complications fed the “vaccine hesitancy” phenomenon, posing a vital communication challenge between the scientific community and public opinion. This review aims to collect and discuss the frequency, management, and outcome of reported neurological complications of COVID-19 vaccines after eighteen months of the World Health Organization’s approval of COVID-19 vaccination, providing an overview of safety and concerns related to the most potent weapon against the SARS-CoV-2.

Myocardial Infarction Following COVID-19 Vaccine Administration: Post Hoc, Ergo Propter Hoc?

Vaccination against coronavirus disease 2019 (COVID-19) is the safest and most effective strategy for controlling the pandemic. However, some cases of acute cardiac events following vaccine administration have been reported, including myocarditis and myocardial infarction (MI). While post-vaccine myocarditis has been widely discussed, information about post-vaccine MI is scarce and heterogenous, often lacking in histopathological and pathophysiological details. We hereby present five cases (four men, mean age 64 years, range 50–76) of sudden death secondary to MI and tightly temporally related to COVID-19 vaccination. In each case, comprehensive macro- and microscopic pathological analyses were performed, including post-mortem cardiac magnetic resonance, to ascertain the cause of death. To investigate the pathophysiological determinants of MI, toxicological and tryptase analyses were performed, yielding negative results, while the absence of anti-platelet factor 4 antibodies ruled out vaccine-induced thrombotic thrombocytopenia. Finally, genetic testing disclosed that all subjects were carriers of at least one pro-thrombotic mutation. Although the presented cases do not allow us to establish any causative relation, they should foster further research to investigate the possible link between COVID-19 vaccination, pro-thrombotic genotypes, and acute cardiovascular events.

Successful Treatment of Immune Thrombocytopenic Purpura with Intracranial Hemorrhaging and Duodenal Bleeding Following SARS-CoV-2 Vaccination

Several vaccines have been developed for coronavirus disease 2019 - caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) - in record time. A few cases of immune thrombocytopenic purpura (ITP) following SARS-CoV-2 vaccination have been reported. We herein report a 90-year-old man who received the Pfizer-BioNTech SARS-CoV-2 vaccine (BNT162b2) and developed severe thrombocytopenia with intracranial hemorrhaging and duodenal bleeding, consistent with vaccine-related ITP. He was successfully treated with intravenous immunoglobulin, prednisolone, and eltrombopag and discharged without cytopenia. Vaccine-related ITP should be suspected in patients presenting with abnormal bleeding or purpura after vaccination.

Case Series of Thrombosis With Thrombocytopenia Syndrome After COVID-19 Vaccination-United States, December 2020 to August 2021

BACKGROUND

Thrombosis with thrombocytopenia syndrome (TTS) is a potentially life-threatening condition associated with adenoviral-vectored COVID-19 vaccination. It presents similarly to spontaneous heparin-induced thrombocytopenia. Twelve cases of cerebral venous sinus thrombosis after vaccination with the Ad26.COV2.S COVID-19 vaccine (Janssen/Johnson & Johnson) have previously been described.

OBJECTIVE

To describe surveillance data and reporting rates of all reported TTS cases after COVID-19 vaccination in the United States.

DESIGN

Case series.

SETTING

United States.

PATIENTS

Case patients receiving a COVID-19 vaccine from 14 December 2020 through 31 August 2021 with thrombocytopenia and thrombosis (excluding isolated ischemic stroke or myocardial infarction) reported to the Vaccine Adverse Event Reporting System. If thrombosis was only in an extremity vein or pulmonary embolism, a positive enzyme-linked immunosorbent assay for antiplatelet factor 4 antibodies or functional heparin-induced thrombocytopenia platelet test result was required.

MEASUREMENTS

Reporting rates (cases per million vaccine doses) and descriptive epidemiology.

RESULTS

A total of 57 TTS cases were confirmed after vaccination with Ad26.COV2.S (n = 54) or a messenger RNA (mRNA)-based COVID-19 vaccine (n = 3). Reporting rates for TTS were 3.83 per million vaccine doses (Ad26.COV2.S) and 0.00855 per million vaccine doses (mRNA-based COVID-19 vaccines). The median age of patients with TTS after Ad26.COV2.S vaccination was 44.5 years (range, 18 to 70 years), and 69% of patients were women. Of the TTS cases after mRNA-based COVID-19 vaccination, 2 occurred in men older than 50 years and 1 in a woman aged 50 to 59 years. All cases after Ad26.COV2.S vaccination involved hospitalization, including 36 (67%) with intensive care unit admission. Outcomes of hospitalizations after Ad26.COV2.S vaccination included death (15%), discharge to postacute care (17%), and discharge home (68%).

LIMITATIONS

Underreporting and incomplete case follow-up.

CONCLUSION

Thrombosis with thrombocytopenia syndrome is a rare but serious adverse event associated with Ad26.COV2.S vaccination. The different demographic characteristics of the 3 cases reported after mRNA-based COVID-19 vaccines and the much lower reporting rate suggest that these cases represent a background rate.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention.

Effects of tai chi and qigong on rehabilitation after COVID-19: a protocol for systematic review and meta-analysis

INTRODUCTION

COVID-19 is a public health emergency of international concern, which is characterised by rapid and widespread transmission, high mortality and complications. Several studies have shown the benefits of tai chi and qigong for recovery after COVID-19; however, no meta-analysis has been reported. Therefore, the purpose of this study is to evaluate the efficacy and safety of tai chi and/or qigong on rehabilitation after COVID-19 through a systematic review and meta-analysis to provide a reference and basis for clinical application.

METHODS AND ANALYSIS

This study will use the Cochrane Library, PubMed, Web of Science, Embase, China Knowledge Network, China Biomedical Literature Database, Chinese Scientific Journal Database and Wanfang Database. The time period is from the inception of the database to November 2021, with no language restrictions. Searches will be conducted using the subject terms "Taichi","Qigong" and "COVID-19" plus free-text words. Articles will be screened and collected by two reviewers independently. Included studies will be assessed for quality using the Cochrane Risk of Bias Assessment Tool. Statistical analyses will be performed using the Revman V.5.3 software. The primary outcomes include 1-second forced expiratory volume and 1-second forced vital capacity, oxygen saturation, total white cell count and quality of life score. Secondary outcomes include time to remission of major symptoms, incidence of adverse events, clinical cure rate and mortality. Subgroup and sensitivity analyses will also be used to explore and interpret the heterogeneity. This protocol is written based on the guideline of the Preferred Reporting Items for Systematic Reviews and Meta-analyses Protocol.

ETHICS AND DISSEMINATION

Ethical approval and consent are unnecessary because no primary data will be collected. The results will be disseminated through peer-reviewed publications.

PROSPERO REGISTRATION NUMBER

CRD42021288962.

Neuro-Ophthalmic Implications of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Related Infection and Vaccination

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic created a unique opportunity to study the effects of infection and vaccination on disease. The year 2020 was dominated by infection and its consequences. The year 2021 was dominated by vaccination and its consequences. It will still take several years for full maturation of databases required for robust epidemiological studies. Therefore, this review on the implications for neuro-ophthalmology draws on resources presently available including reported adverse reactions to vaccination. Illustrative clinical cases are presented.The spectrum of pathology following infection with SARS-CoV-2 falls into 4 main categories: autoimmune, vascular, sequelae of brain damage, and miscellaneous. This review is exhaustive, but the most common conditions discussed relate to headaches and associated symptoms; vertigo, diplopia, and nystagmus; vascular complications of the eye and brain; cranial nerve (mono-)neuropathies; photophobia, ocular discomfort, and optic neuritis. Of the 36 main adverse reactions reviewed, vaccine-induced immune thrombotic thrombocytopenia is a novel complication requiring specific hematological management. Updated diagnostic criteria are summarized. It is relevant to remember taking a medication history because of side effects and to recognize the relevance of comorbidities. The clinical assessment can frequently be performed virtually. Consensus recommendations on telemedicine and the virtual assessment are summarized in a practical and compressed format.The review concludes with an epidemiological tetralogy to interrogate, in future studies, associations with (1) SARS-CoV-2 pandemic infection, (2) SARS-CoV-2 worldwide vaccination, and (3) the possibility of a rebound effect of infections in the pandemic aftermath.

Cerebral Venous Thrombosis

Cerebral venous thrombosis (CVT) is a rare form of stroke that often affects younger age groups, especially reproductive age group females. CVT is a potentially fatal neurological condition that can be frequently overlooked due to the vague nature of its clinical and radiological presentation. Headache is the most common presenting symptom. However, a wide range of symptoms can be present and the symptom onset can be acute, subacute, or chronic. Neuroimaging is mandatory in cases where CVT is suspected. Both magnetic resonance venography and computed tomography venography can confirm a diagnosis of CVT. Anticoagulation with low-molecular-weight heparin is the mainstay of treatment. Intracranial hemorrhage is not considered a contraindication to the use of anticoagulants in CVT. Endovascular intervention is still controversial but can be a treatment option for patients with neurological deterioration or thrombus progression, despite the use of anticoagulation or with development of new or worsening intracerebral hemorrhage. Patients with CVT have an increased risk of recurrence of CVT and other types of venous thromboembolism. This review provides an overview of the epidemiology, diagnosis, and treatment of CVT in adults. Commentary about increased presentation of CVT in patients with coronavirus disease 2019 (COVID-19), or after immunization against COVID-19, is also provided.

Antibodies against Platelet Factor 4 and Their Associated Pathologies: From HIT/HITT to Spontaneous HIT-Like Syndrome, to COVID-19, to VITT/TTS

Antibodies against platelet factor 4 (PF4), a protein released from alpha-granules of activated platelets, may cause a number of pathophysiological conditions. The most commonly known is heparin-induced thrombocytopenia (HIT), which develops in a small proportion of people treated with the anticoagulant drug heparin. Notably, PF4 binds with high affinity to heparin, and in HIT, complexes of PF4/H may, in a small proportion of susceptible patients, trigger the development of anti-PF4 antibodies and subsequent platelet activation and aggregation, ultimately leading to the development of pathological thrombosis at sites of vessel occlusion. Of more modern interest, antibodies against PF4 may also arise in patients with COVID-19 (Coronavirus Disease 2019) or in patients who have been vaccinated against COVID-19, especially in recipients of adenovirus-based vaccines. For this latter group of patients, the terms VITT (vaccine-induced [immune] thrombotic thrombocytopenia) and TTS (thrombotic thrombocytopenia syndrome) have been coined. Another category associated with this pathophysiology comprises those in whom a precipitating event is not clear; this category is referred to as ‘spontaneous HIT-like syndrome’. Despite its name, it arises as an HIT-mimicking disorder but without antecedent heparin exposure. In this narrative review, we describe the development of antibodies against PF4, and associated pathophysiology, in such conditions.

Immunogenicity after Second ChAdOx1 nCoV-19 (AZD1222) Vaccination According to the Individual Reactogenicity, Health Status and Lifestyle

The immune-acquired responses after vaccination vary depending on the type of vaccine and the individual. The purpose of this study was to investigate the relationship between the acquisition of immunity and the side effects, health status, and lifestyle after completion of the second dose of AZD1222. Blood samples were collected after a second dose of AZD1222. The Euroimmun Anti-SARS-CoV-2 ELISA (IgG) for anti-S1 antibody, the cPASS SARS-CoV-2 neutralizing antibody detection kit for the surrogate virus neutralization test, and the T-spot Discovery SARS-CoV-2 kit were used to identify cellular immunogenicity. Patient experience of adverse effects was investigated using questionnaires. Information on health status and lifestyle were collected from the most recent health checkup data. Generally, females experience more reactogenicity in both intensity and duration. The rash of the first shot and chills of the second shot were associated with humoral immunity. However, comprehensive adverse effects had no correlation with humoral and cellular immunity. The T-spot-positive group had a higher creatinine level, which reflects muscle mass, than the T-spot-negative group. Males presented a higher level of T-spot assays. Body mass index and age were negatively correlated with the T-spot assay and anti-S1 antibody, respectively. Immune acquisition after the second AZD1222 shot was not associated with reactogenicity. However, individuals’ sex, age, and BMI were found to be associated with immunogenicity after vaccination.