Reduced platelet glycoprotein Ibα shedding accelerates thrombopoiesis and COX-1 recovery: implications for aspirin dosing regimen.

Cardiovascular (CV) disease prevention with low-dose aspirin can be less effective in patients with a faster recovery of platelet (PLT) cyclooxygenase (COX)-1 activity during the 24-hour dosing interval. We previously showed that incomplete suppression of TXA2 over 24 hours can be rescued by a twice daily aspirin regimen. Here we show that reduced PLT glycoprotein (GP)Ibα shedding characterizes patients with accelerated COX-1 recovery and may contribute to higher thrombopoietin (TPO) production and higher rates of newly formed PLT, escaping aspirin inhibition over 24 hours. Two hundred aspirin-treated patients with high CV risk (100 with type 2 diabetes mellitus) were stratified according to the kinetics of PLT COX-1 activity recovery during the 10- to 24-hour dosing interval. Whole proteome analysis showed that PLT from patients with accelerated COX-1 recovery were enriched in proteins involved in cell survival, inhibition of apoptosis and cellular protrusion formation. In agreement, we documented increased plasma TPO, megakaryocyte maturation and proplatelet formation, and conversely increased PLT galactose and reduced caspase 3, phosphatidylserine exposure and ADAM17 activation, translating into diminished GPIbα cleavage and glycocalicin (GC) release. Treatment of HepG2 cells with recombinant GC led to a dose-dependent reduction of TPO mRNA in the liver, suggesting that reduced GPIbα ectodomain shedding may unleash thrombopoiesis. A cluster of clinical markers, including younger age, non-alcoholic fatty liver disease, visceral obesity and higher TPO/GC ratio, predicted with significant accuracy the likelihood of faster COX-1 recovery and suboptimal aspirin response. Circulating TPO/GC ratio, reflecting a dysregulation of PLT lifespan and production, may provide a simple tool to identify patients amenable to more frequent aspirin daily dosing.

Direct oral anticoagulant plasma levels in hospitalized COVID-19 patients treated with dexamethasone.

Direct oral anticoagulants (DOACs) are not recommended in COVID-19 patients receiving dexamethasone because of potential drug-drug and drug-disease interactions affecting anticoagulant concentration and activity. To evaluate short- and long-term pharmacokinetic interactions, serial through and peak DOAC plasma levels were prospectively measured during and after dexamethasone therapy, as well as during the acute phase and after recovery from COVID-19 in hospitalized, non-critically ill patients undergoing treatment with DOACs. Thirty-three (18 males, mean age 79 years) consecutive patients received DOACs (17 apixaban, 12 rivaroxaban, 4 edoxaban) for atrial fibrillation (n = 22), venous thromboembolism (n = 10), and acute myocardial infarction (n = 1). Twenty-six patients also received dexamethasone at a dose of 6 mg once daily for a median of 14 days. Trough DOAC levels on dexamethasone were within and below expected reference ranges respectively in 87.5 and 8.3% of patients, with no statistically significant differences at 48-72 h and 14-21 days after dexamethasone discontinuation. Peak DOAC levels on dexamethasone were within expected reference ranges in 58.3% of patients, and below ranges in 33.3%, of whom over two thirds had low values also off dexamethasone. No significant differences in DOAC levels were found during hospitalization and after resolution of COVID-19. Overall, 28 patients were discharged alive, and none experienced thrombotic or bleeding events. In this study, dexamethasone administration or acute COVID-19 seemed not to affect DOAC levels in hospitalized, non-critically ill COVID-19 patients.

Basophil Activation Test with Different Polyethylene Glycols in Patients with Suspected PEG Hypersensitivity Reactions.

Allergic reactions to COVID-19 vaccine components are rare but should be considered. Polyethylene glycol (PEG) is responsible for anaphylaxis in mRNA vaccines. Skin tests have been used in the allergological work-up programs for COVID-19 vaccine evaluation. However, the reproducibility of the skin prick test is time-dependent and the reactivity declines over time. Therefore, we combined the administration of the skin tests with the basophil activation test (BAT) using PEG2000, PEG4000 and DMG-PEG2000, where the BAT was considered positive when the percentage of activated basophils was higher than 6%, 5% and 6.5%, for PEG 4000, PEG2000 and DMG-PEG2000, respectively. To this end, among the subjects that underwent allergy counseling at the Allergy Unit of our Institution during the 2020/2021 vaccination campaign, 13 patients had a suggested medical history of PEG/drug hypersensitivity and were enrolled together with 10 healthy donors. Among the enrolled patients 2 out of 13 tested patients were positive to the skin test. The BAT was negative in terms of the percentages of activated basophils in all analyzed samples, but the stimulation index (SI) was higher than 2.5 in 4 out of 13 patients. These data evidenced that, when the SI is higher than 2.5, even in the absence of positivity to BAT, the BAT to PEG may be a useful tool to be coupled to skin tests to evidence even low-grade reactions.

Role of CES1 and ABCB1 Genetic Polymorphisms on Functional Response to Dabigatran in Patients with Atrial Fibrillation.

Background: Dabigatran etexilate is a pro-drug hydrolyzed into dabigatran by carboxylesterases (CES) and is a substrate of the P-Glycoprotein encoded by the adenosine-triphosphate-binding cassette sub-family B member (ABCB)1 genes. We evaluated the functional response to dabigatran according to different CES1 and ABCB1 single-nucleotide polymorphisms (SNPs) in patients with atrial fibrillation (AF). Methods: A total of 100 consecutive patients with AF taking dabigatran were enrolled by two Italian centers. A venous blood sample was drawn for genetic determinations, as well as a measurement of the diluted thrombin time (dTT) and drug plasma concentrations, at the trough and peak. The main objective was the relationship between the dTT values and CES1 rs2244613, CES1 rs8192935 and ABCB1 rs4148738 SNP while on two different dabigatran doses (110 and 150 mg BID). Results: A total of 43 patients were on a 110 mg dabigatran dose and 57 on 150 mg. The DTT values at the trough and at peak were not different among patients with different CES1 rs2244613 and CES1 rs8192935 genotypes, regardless of the dabigatran dose. In patients on 150 mg dabigatran, the dTT values at the trough were 77 (44-111) ng/mL in patients with the ABCB1 rs4148738 heterozygous CT genotype vs. 127 (85-147) ng/mL in the wild-type CC genotype vs. 110 (47-159) ng/mL in the mutant trait TT genotype (p = 0.048). In patients with the ABCB1 rs4148738 CT genotype, OR for having dTT values at a trough below the median was 3.21, 95% CI 1.04-9.88 (p = 0.042). Conclusions: ABCB1 rs4148738 CT heterozygous is associated with the reduced anticoagulant activity of dabigatran at the trough in patients receiving the higher dose regimen.

Anamnestic frailty phenotype and adverse outcomes in patients treated with direct oral anticoagulants: Validation and comparative performance with frailty phenotype.

AIMS: The anamnestic frailty phenotype (AFP) is a quick, instrument-free tool derived from frailty phenotype (FP). We prospectively evaluated the discriminative capacity and prognostic value of AFP in ambulatory patients receiving DOACs for atrial fibrillation (AF) or venous thromboembolism (VTE), and compared AFP performance with that of FP. METHODS AND RESULTS: Sensitivity, specificity, positive and negative predictive value (PPV, NPV) with corresponding 95% confidence intervals (95%CI), were estimated for bleeding, thromboembolism, and all-cause mortality. Risk ratios (RRs) were calculated in frail versus non-frail patients. Of 236 patients (median age 78 years), 98 (42%) and 89 (38%) were classified as frail according to FP and AFP, respectively (Kappa= 0.76). Frailty, as assessed by AFP, was associated with higher risk of bleeding (RR 2.3; 95%CI, 1.2 to 4.6), and mortality (RR 4.4; 95%CI, 1.3 to 19.7). Similarly, to FP, AFP exhibited modest sensitivity and specificity, but high NPV that was 91% (95%CI, 85 to 95) for bleeding, 98% (95%CI, 94 to 100) for thromboembolism, and 98% (95%CI, 94 to 100) for mortality. CONCLUSION: Among patients receiving DOACs for AF or VTE, AFP was associated with an increased risk of adverse outcomes. AFP exhibited modest sensitivity and specificity, but excellent NPV. If confirmed, these findings suggest that AFP may represent a rapid, easy-to-use and unexpensive tool that may potentially help identify patients at lower risk for adverse outcomes and tailor anticoagulation management.