Significant association of anti-platelet factor 4/heparin antibody with cardiovascular disease in hemodialysis patients: a longitudinal 7-year study

Risk of Thrombosis Following the First Dose of ChAdOx1 nCoV-19 Vaccine in Patients Undergoing Maintenance Hemodialysis: A Self-Controlled Case Series Study

Background

The ChAdOx1 nCoV-19 vaccine is associated with vaccine-induced thrombosis and thrombocytopenia (VITT). Patients with end-stage renal disease (ESRD) under hemodialysis are at elevated risk of heparin-induced thrombocytopenia, which shares similar mechanisms with VITT. We aimed to examine the risk of VITT after the first dose of ChAdOx1 nCoV-19 vaccine using a self-controlled case series analysis (SCCS) in the hemodialyzed ESRD population.

Methods

Drawing from the largest multi-center electronic medical records database in Taiwan, we identified adult patients, with or without hemodialysis, between 1st December, 2020, and 31st December, 2021, who received a first dose of ChAdOx1 nCoV-19 vaccine and had an outcome of thrombocytopenia, venous thrombosis, or arterial thrombosis. We calculated the incident rate ratios (IRRs) of outcomes in different periods at risk, compared to periods not at risk.

Results

 We identified 59 hemodialysis patients and 41 non-dialysis patients with an outcome. The SCCS analyses showed, for the hemodialysis group, a significantly increased risk of outcomes during the period 31 to 60 days post-exposure to ChAdOx1 nCoV-19 vaccine (IRR: 2.823; 95% CI: 1.423-5.600). However, in non-dialysis patients there was no increase in risks during any of the post-exposure risk periods.

Conclusion

For ESRD patients under hemodialysis, the first dose of ChAdOx1 nCoV-19 vaccine was associated with a 2.8-fold increase in risk of thrombosis.

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.

Anticoagulation in hemodialysis: A narrative review

Systemic anticoagulation in maintenance hemodialysis (HD) has historically been considered necessary to maintain the extracorporeal circuit (ECC) and preserve dialysis efficiency. Unfractionated heparin (UFH) is the most commonly used anticoagulant due to low cost and staff familiarity. Despite widespread use, there is little standardization of heparin dosing protocols in the United States. Although the complication rates with UFH are low for the general population, certain contraindications have led to exploration in alternative anticoagulants in patients with end-stage kidney disease (ESKD). Here we review the current evidence regarding heparin dosing protocols, complications associated with heparin use, and discuss alternatives to UFH including anticoagulant-free routine HD.

Neutrophil-to-lymphocyte ratio and red blood cell distribution width-to-platelet ratio predict cardiovascular events in hemodialysis patients

Cardiovascular diseases are among the primary causes of decreased quality of life as well as mortality of hemodialysis patients with end-stage renal disease. The aim of the present study was to evaluate the predictive value of the red blood cell distribution width (RDW)-to-platelet ratio (RPR) and neutrophil-to-lymphocyte ratio (NLR) regarding the occurrence or development of cardiovascular events in hemodialysis patients, as well as the prognostic value of this metric. A total of 219 hemodialysis patients with cardiovascular events (HCE group) and 276 hemodialysis patients with no cardiovascular events (HNCE group) were enrolled in the present study. The clinical characteristics and laboratory parameters on admission, including RDW, as well as neutrophil, lymphocyte and platelet counts, were recorded. The NLR and RPR were increased in the HCE group compared with those in the HNCE group and there was a positive association between the NLR or RPR and the incidence of cardiovascular events in hemodialysis patients. In the receiver operating characteristics curve analysis, the area under the curve of the RPR for predicting cardiovascular events in hemodialysis patients was 0.88, while that for the NLR was 0.84. The sensitivity and specificity of the RPR for predicting cardiovascular events in hemodialysis patients were 0.87 and 0.82 respectively, and for the NLR, they were 0.75 and 0.79, respectively. The RPR was an independent risk factor for the prognosis regarding cardiovascular events in hemodialysis patients. In addition, the NLR and RPR were correlated with brain natriuretic peptide (BNP), cardiac troponin I (cTnI), creatine kinase isoenzyme-MB (CK-MB), and associated with ST segment changes in HCE patients. In conclusion, it was possible to predict the incidence of cardiovascular events in hemodialysis patients using the NLR and RPR, while the RPR had a better sensitivity and specificity than the NLR. The RPR was an independent risk factor for the prognosis regarding cardiovascular events in hemodialysis patients. These routinely available parameters should be considered as novel diagnostic markers for the occurrence and development of cardiovascular events in hemodialysis patients and their prognosis.