Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder mediated by platelet-activating antibodies that target complexes of platelet factor 4 (PF4) and heparin. Because nearly all patients undergoing cardiopulmonary bypass (CPB) are exposed to heparin and experience a postoperative platelet count fall, it is not surprising that HIT is commonly suspected in this population. However, the incidence of HIT in cardiac surgery patients who receive intraoperative and postoperative unfractionated heparin is much lower than the incidence of suspected HIT, being approximately 1 to 2%. Clinical diagnosis may therefore be particularly challenging because of the need to distinguish the common platelet count fall associated with CPB and surgery from the much less common platelet count fall associated with HIT. A biphasic platelet count pattern is characteristic of HIT in this setting. Laboratory diagnosis is also difficult because of the high frequency of anti-PF4/heparin antibody seropositivity after cardiac surgery in patients without HIT. A unique aspect of management in the cardiac surgery setting is selecting an anticoagulant for intraoperative use in patients with a history of HIT who require cardiac surgery. In this article, we review the epidemiology, clinical diagnosis, and laboratory diagnosis of HIT in cardiac surgery patients and present a conceptual framework for selecting intraoperative anticoagulation in patients with a history of HIT.

Objectives CD8T cells lacking CD28 were originally reported by Wedderburn and colleagues as a characteristic feature of JIA, but the relevance of these unusual cells to JIA remains to be elucidated. Because of recent evidence that CD28 loss is typical of terminally differentiated lymphocytes, we examined for functional subsets of CD8T cells in JIA. Methods Following informed consent/assent, blood and/or waste synovial fluid were collected from children with definite diagnosis of JIA (n = 98). De-identified blood (n = 33) and cord blood (n = 13) samples from healthy donors were also collected. CD8T and CD4T cells were screened for novel receptors, and where indicated, bioassays were performed to determine functional relevance of the identified receptor. Results Patients had a naïve T cell compartment with shortened telomeres, and their entire T cell pool had reduced proliferative capacity. They had an over abundance of CD31+CD28null CD8T cells, which was a significant feature of oligoarticular JIA (n = 62) compared to polyarticular JIA (n = 36). CD31+CD28null CD8T cells had limited mitotic capacity, and expressed high levels of the senescence antigens γH2Ax and/or p16. Ligation of CD31, independent of the TCR, sufficiently induced tyrosine phosphorylation, vesicle exocytosis, and production of IFN-γ and IL-10. Conclusion These data provide the first evidence for cell senescence, represented by CD31+CD28null CD8T cells, in the pathophysiology of JIA. Activation of these unusual cells in a TCR-independent manner suggests they are maladaptive, and could be potential targets for immunotherapy.

Background The presence of a hypercoagulable disorder such as heparin‐induced thrombocytopenia (HIT) may protect against anticoagulant‐associated bleeding. Objectives To determine the incidence of major bleeding in patients with suspected HIT. Methods We performed a retrospective analysis of 310 patients suspected of having HIT from the Hospital of the University of Pennsylvania and an affiliated community hospital. We compared the cumulative incidence of major bleeding following suspicion for HIT by ultimate HIT status (HIT+ or HIT−) and exposure to an alternative anticoagulant (Tx+ or Tx−). Secondary outcomes included the incidence of new/progressive thrombosis and 30‐day mortality. Results The incidence of major bleeding was high in the HIT+Tx+, HIT− Tx+, and HIT−Tx− groups (35.7%, 44.0%, and 37.3%, respectively). The time to first major bleeding event did not differ between groups (P = .24). Factors associated with increased risk of major bleeding included intensive care unit admission (HR 2.24, 95% CI 1.44‐3.47), platelet count < 25 × 109/L (HR 2.13, 1.10‐4.12), and renal dysfunction (HR 1.56, 1.06‐2.27); 35.7% of HIT+Tx+, 13.8% HIT−Tx+, and 9.3% of HIT−Tx− patients experienced new or progressive thrombosis. Mortality was similar among the three groups (26.2% HIT+Tx+, 34.5% HIT−Tx+, and 26.7% of HIT−Tx− [P = .34]). Conclusions Among patients with suspected HIT, major bleeding was common regardless of HIT status. Contrary to our hypothesis, HIT+ patients were not protected from major bleeding. A better understanding of bleeding risk is needed to inform management decisions in patients with suspected HIT.

The HIT Expert Probability (HEP) score compared favorably with the 4Ts score in a retrospective study. We assessed the diagnostic accuracy of the HEP score compared with the 4Ts score in a prospective cohort of 310 patients with suspected heparin-induced thrombocytopenia (HIT). A member of the clinical team calculated the HEP score and 4Ts score. An independent panel adjudicated HIT status based on a clinical summary as well as the results of HIT laboratory testing. The prevalence of HIT in the study population was 14.7%. At a cutoff of ≥3, the HEP score was 95.3% sensitive (95% confidence interval [CI], 84.2-99.4) and 35.7% specific (95% CI, 29.8-42.0) for HIT. A 4Ts score of ≥4 had a sensitivity of 97.7% (95% CI, 86.2-99.8) and specificity of 32.9% (95% CI, 27.2-39.1). The areas under the receiver operating characteristic (ROC) curves (AUCs) for the HEP score and 4Ts score were similar (0.81 [95% CI, 0.74-0.87] vs 0.76 [95% CI, 0.69-0.83]; P = .12). The HEP score exhibited a significantly higher AUC than the 4Ts score in patients in the intensive care unit (ICU) (0.86 vs 0.79; P = .03). Among trainee scorers, the HEP score performed significantly better than the 4Ts score (AUC, 0.80 vs 0.73; P = .03). Our data suggest that either the 4Ts score or the HEP score may be used in clinical practice. The HEP score may be preferable in ICU patients and among less experienced clinicians.

Summary Background There are conflicting data on whether the IgG-specific or polyspecific antiplatelet factor 4/heparin (PF4/H) enzyme-linked immunosorbent assay (ELISA) is preferred for the laboratory diagnosis of heparin-induced thrombocytopenia (HIT). Objectives To directly compare diagnostic accuracy of IgG-specific versus polyspecific ELISA in HIT. Patients/Methods A systematic search yielded nine studies comprising 1948 patients with suspected HIT tested by both IgG-specific and polyspecific ELISAs and a reference standard against which the diagnostic accuracy of the ELISAs could be measured. Study quality was assessed by QUADAS-2 criteria. Results There was identical sensitivity for IgG-specific and polyspecific ELISAs (0.97; 95% confidence interval (CI), 0.95–0.99) and superior specificity of IgG-specific compared with polyspecific ELISA (0.87 [0.85–0.88] vs. 0.82 [0.80–0.84], respectively). Performance was similar in subgroups using the serotonin release assay and a single commercial ELISA manufacturer. The negative predictive values of IgG-specific and polyspecific ELISA were similarly high (0.99, [0.99–1.00], but the positive predictive value was superior with IgG-specific compared with polyspecific ELISA (0.56 [0.52–0.61] vs. 0.32 [0.28–0.35], respectively). The positive likelihood ratio (LR) was higher in IgG-specific than polyspecific ELISA, although negative LRs were similar. There was high risk of quality concerns in domains of index test and reference standard. Conclusions The superior diagnostic accuracy of IgG-specific ELISA reinforces the ISTH-SSC recommendation for standardization of laboratory testing for HIT. Likelihood ratios of individual assays may be used in combination with clinical scoring systems as part of an integrated diagnostic algorithm for HIT.

Immunotherapy is an evolving modality in the treatment of non-Hodgkin lymphoma. Vaccinations with patient-specific tumor-derived antigens have been developed to strengthen immune response to tumor. The success of rituximab, a monoclonal antibody for CD20 on malignant B-cells, fueled further immunotherapy research. The power of the immune system to fight hematologic malignancies is seen in allogeneic stem cell transplant, where donor T cells attack residual malignant cells in the recipient. Now, three innovative therapeutic immunotherapy classes (I) adoptive cellular therapy; (II) immune-checkpoint inhibitors; and (III) novel antibody therapies show promising results in non-Hodgkin lymphoma. Genetically engineered T cells, CAR T cells, obtained remissions in lymphomas refractory to conventional chemotherapy. Immune-checkpoint inhibitors, such as nivolumab and pembrolizumab revolutionized the treatment of many solid tumors, and unprecedented results are now reported in relapsed/refractory lymphoma. Building on the success of rituximab, additional therapeutic monoclonal antibodies were developed for lymphoma treatment. Antibodies have recently been further engineered with multiple binding sites to directly engage both tumor and T cells. There are exciting early clinical trial results for the first bispecific T-cell engager (BiTE), blinatumomab, as well as promising ongoing studies for dual antibody molecules, Dual-Affinity Re-Targeting (DART) proteins. This review highlights these three immunotherapy classes for relapsed/refractory non-Hodgkin lymphomas and discusses the mechanism of action, clinical efficacy, and toxicities of each.

In acquired hemophilia A (AHA), autoantibodies to coagulation factor VIII (FVIII) neutralize FVIII activity leading to a potentially severe bleeding diathesis that carries a high rate of morbidity and mortality. This disorder is rare and occurs mainly in adults over 60 years of age or in the postpartum period. The diagnosis should be suspected in patients with new-onset bleeding without a personal or family history of bleeding and can be confirmed via specific assays for FVIII inhibitors. Treatment involves both hemostatic therapies to decrease bleeding and immune modulation strategies to re-establish immune tolerance to FVIII. There are limited data on treatment for refractory disease, based mostly on small case series. Registry studies have informed consensus guidelines for optimal hemostatic therapies and initial immunosuppressive therapies. Additional studies are needed to evaluate novel hemostatic agents and develop biomarkers to risk-stratify treatment while limiting adverse events.

ImportanceThe incidence of arterial thromboembolism and venous thromboembolism in persons with COVID-19 remains unclear.ObjectiveTo measure the 90-day risk of arterial thromboembolism and venous thromboembolism in patients hospitalized with COVID-19 before or during COVID-19 vaccine availability vs patients hospitalized with influenza.Design, Setting, and ParticipantsRetrospective cohort study of 41 443 patients hospitalized with COVID-19 before vaccine availability (April-November 2020), 44 194 patients hospitalized with COVID-19 during vaccine availability (December 2020-May 2021), and 8269 patients hospitalized with influenza (October 2018-April 2019) in the US Food and Drug Administration Sentinel System (data from 2 national health insurers and 4 regional integrated health systems).ExposuresCOVID-19 or influenza (identified by hospital diagnosis or nucleic acid test).Main Outcomes and MeasuresHospital diagnosis of arterial thromboembolism (acute myocardial infarction or ischemic stroke) and venous thromboembolism (deep vein thrombosis or pulmonary embolism) within 90 days. Outcomes were ascertained through July 2019 for patients with influenza and through August 2021 for patients with COVID-19. Propensity scores with fine stratification were developed to account for differences between the influenza and COVID-19 cohorts. Weighted Cox regression was used to estimate the adjusted hazard ratios (HRs) for outcomes during each COVID-19 vaccine availability period vs the influenza period.ResultsA total of 85 637 patients with COVID-19 (mean age, 72 [SD, 13.0] years; 50.5% were male) and 8269 with influenza (mean age, 72 [SD, 13.3] years; 45.0% were male) were included. The 90-day absolute risk of arterial thromboembolism was 14.4% (95% CI, 13.6%-15.2%) in patients with influenza vs 15.8% (95% CI, 15.5%-16.2%) in patients with COVID-19 before vaccine availability (risk difference, 1.4% [95% CI, 1.0%-2.3%]) and 16.3% (95% CI, 16.0%-16.6%) in patients with COVID-19 during vaccine availability (risk difference, 1.9% [95% CI, 1.1%-2.7%]). Compared with patients with influenza, the risk of arterial thromboembolism was not significantly higher among patients with COVID-19 before vaccine availability (adjusted HR, 1.04 [95% CI, 0.97-1.11]) or during vaccine availability (adjusted HR, 1.07 [95% CI, 1.00-1.14]). The 90-day absolute risk of venous thromboembolism was 5.3% (95% CI, 4.9%-5.8%) in patients with influenza vs 9.5% (95% CI, 9.2%-9.7%) in patients with COVID-19 before vaccine availability (risk difference, 4.1% [95% CI, 3.6%-4.7%]) and 10.9% (95% CI, 10.6%-11.1%) in patients with COVID-19 during vaccine availability (risk difference, 5.5% [95% CI, 5.0%-6.1%]). Compared with patients with influenza, the risk of venous thromboembolism was significantly higher among patients with COVID-19 before vaccine availability (adjusted HR, 1.60 [95% CI, 1.43-1.79]) and during vaccine availability (adjusted HR, 1.89 [95% CI, 1.68-2.12]).Conclusions and RelevanceBased on data from a US public health surveillance system, hospitalization with COVID-19 before and during vaccine availability, vs hospitalization with influenza in 2018-2019, was significantly associated with a higher risk of venous thromboembolism within 90 days, but there was no significant difference in the risk of arterial thromboembolism within 90 days.