Introduction: D-dimer assay, generally evaluated according to cutoff points calibrated for VTE exclusion, is used to estimate the individual risk of recurrence after a first idiopathic event of venous thromboembolism (VTE). Methods: Commercial D-dimer assays, evaluated according to predetermined cutoff levels for each assay, specific for age (lower in subjects <70 years) and gender (lower in males), were used in the recent DULCIS study. The present analysis compared the results obtained in the DULCIS with those that might have been had using the following different cutoff criteria: traditional cutoff for VTE exclusion, higher levels in subjects aged ≥60 years, or age multiplied by 10. Results: In young subjects, the DULCIS low cutoff levels resulted in half the recurrent events that would have occurred using the other criteria. In elderly patients, the DULCIS results were similar to those calculated for the two age-adjusted criteria. The adoption of traditional VTE exclusion criteria would have led to positive results in the large majority of elderly subjects, without a significant reduction in the rate of recurrent event. Conclusion:The results confirm the usefulness of the cutoff levels used in DULCIS.

Background Antiviral drugs are administered in patients with severe COVID‐19 respiratory syndrome, including those treated with direct oral anticoagulants (DOACs). Concomitant administration of antiviral agents has the potential to increase their plasma concentration. A series of patients managed in the Cremona Thrombosis Center were admitted at Cremona Hospital for SARS‐CoV‐2 and started antiviral drugs without stopping DOAC therapy. DOAC plasma levels were measured in hospital and results compared with those recorded before hospitalization. Methods All consecutive patients on DOACs were candidates for administration of antiviral agents (lopinavir, ritonavir, or darunavir). Plasma samples for DOAC measurement were collected 2to 4 days after starting antiviral treatment, at 12 hours from the last dose intake in patients on dabigatran and apixaban, and at 24 hours in those on rivaroxaban and edoxaban. For each patient, C‐trough DOAC level, expressed as ng/mL, was compared with the one measured before hospitalization. Results Of the 1039 patients hospitalized between February 22 and March 15, 2020 with COVID‐19 pneumonia and candidates for antiviral therapy, 32 were on treatment with a DOAC. DOAC was stopped in 20 and continued in the remaining 12. On average, C‐trough levels were 6.14 times higher during hospitalization than in the pre‐hospitalization period. Conclusion DOAC patients treated with antiviral drugs show an alarming increase in DOAC plasma levels. In order to prevent bleeding complications, we believe that physicians should consider withholding DOACs from patients with SARS‐CoV‐2 and replacing them with alternative parenteral antithrombotic strategies for as long as antiviral agents are deemed necessary and until discharge.

Introduction: Direct oral anticoagulant (DOAC) intra-and inter-individual variability was previously reported, but its magnitude is still considered negligible for patient management. Objective: To evaluate inter-and intra-individual variability in real-world atrial fibrillation patients on dabigatran, rivaroxaban or apixaban in four Italian anticoagulation clinics and to assess the correlation between DOAC plasma concentration and creatinine-clearance (CrCl). Materials and Methods: A total of 330 consecutive patients were enrolled, of which 160 were on dabigatran (70 and 90 taking 150 mg or 110 mg twice-daily, respectively), 71 on rivaroxaban (37 and 34 taking 20 mg or 15 mg once-daily) and 99 on apixaban (73 and 26 taking 5 mg or 2.5 mg twice-daily). Blood was taken at trough and peak within the first month (15-25 days) of treatment. Diluted-thrombin-time (dTT) calibrated for dabigatran and anti-FXa calibrated for rivaroxaban or apixaban was performed. Results: Mean inter-individual variability expressed as overall CV values for all drugs was lower at peak (CV = 46%) than at trough (CV = 63%). Mean CV% intra-individual variability was 36.6% at trough and 34.0% at peak. Correlation with CrCl was poor for all drugs and only dabigatran at trough showed a significant correlation. Conclusion: This multicenter study confirms high DOAC inter-individual variability that cannot be explained by the rate of renal clearance to which the three DOAC were subjected since the correlation with CrCl was relatively poor. This poor correlation suggests caution in using CrCl as the sole laboratory parameter to indirectly evaluate residual circulating DOAC.

Background Direct oral anticoagulants (DOACs) are administered at fixed doses without the need for dose adjustment according to laboratory testing. High interindividual variability in drug blood levels has been shown with all DOACs. To evaluate a possible relationship between DOAC C-trough anticoagulant levels and thromboembolic events, 565 consecutive naive patients with atrial fibrillation (AF) were enrolled in this study performed within the START Laboratory Registry. Methods DOAC-specific measurements (diluted thrombin time or anti-activated factor II calibrated for dabigatran; anti-activated FX calibrated for rivaroxaban or apixaban) at C-trough were performed locally at steady state within 15-25 days after the start of treatment. For each DOAC, the interval of C-trough levels, from the limit of quantification to the highest value, was subdivided into four equal classes, and results were attributed to these classes; the median values of results were also calculated. Thromboembolic complications occurring during 1 year of follow-up were recorded. Results Thromboembolic events (1.8%) occurred in 10 patients who had baseline C-trough levels in the lowest class of drug levels. The incidence of thromboembolic events among patients with DOAC C-trough levels in the lowest level class was 2.4%, and that in the remaining groups was 0%. The patients with thrombotic complications also had a higher mean CHA DS -VASc score than that of the total patient population: 5.3 (95% confidence interval [CI] 4.3-6.3 versus 3.0 (95% CI 2.9-3.1). Conclusion In this study cohort, thrombotic complications occurred only in DOAC-treated AF patients who had very low C-trough levels, with a relatively high CHA DS -VASc score. Larger studies are warranted to confirm these preliminary observations.

The development of COVID-19 syndrome in anticoagulated patients, and especially their admission to intensive-care units with acute severe respiratory syndrome (SARS-CoV-2), expose them to specific problems related to their therapy, in addition to those associated with the acute viral infection. Patients on VKA hospitalized with SARS-CoV-2 show high instability of PT INR due to the variability of vitamin K metabolism, diet, fasting, co-medications, liver impairment, and heart failure. Patients on DOAC are exposed to under/over treatment caused by significant pharmacological interferences. In consideration of the pharmacological characteristics of oral anticoagulant drugs, the multiple pharmacological interactions due to the treatment of acute disease and the possible necessity of mechanical ventilation with hospitalization in intensive-care units, we suggest replacing oral anticoagulant therapies (VKA and DOAC) with parenteral heparin to avoid the risk of over/under treatment.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Essentials Currently, DOACs are given at fixed doses and do not require laboratory monitoring.Direct oral anticoagulant‐specific measurements were performed at trough and peak.Patients who developed bleeding events showed higher DOAC plasma levels at peak.This study suggests the need of a more accurate DOAC dose assessment. BackgroundDirect oral anticoagulants (DOACs) are administered at fixed dose. The aim of the study was to evaluate the relationship between DOAC C‐trough or C‐peak plasma levels and bleeding complications in patients with non‐valvular atrial fibrillation (NVAF).MethodsFive hundred sixty five consecutive naive NVAF patients were enrolled. The DOAC measurements at C‐trough and at C‐peak (available in 411 patients) were performed at steady state, within the first month of treatment. Major bleeding (MB), clinically relevant non‐major bleeding (CRNMB), and minor bleeding (MinB), occurring during 1 year of follow‐up after blood sampling, were recorded. For each DOAC, interval of C‐trough and C‐peak levels was subdivided into four equal classes and results were attributed to these classes; the median values of results were also calculated.ResultsTwo hundred eight patients were on apixaban, 185 on dabigatran, and 172 on rivaroxaban. For 1‐[qqqdeletezzz] year follow up for all patients, we observed: 19 MB (3.36%), 6 CRNMB (1.06%), and 47 MinB (8.31%). The prevalence of bleeding patients with anticoagulant levels in the upper classes of C‐peak activity (II + III + IV) was higher than that in the lowest class. Normalized results of C‐peak levels were higher in patients with bleeding than in those without bleeding.ConclusionsBleeding complications during DOAC treatment were more frequent among atrial fibrillation (AF) patients with higher C‐peak anticoagulant levels. In addition to a previous study that showed an increased risk of thrombotic complications in the patients with low C‐trough levels, this study seems to indicate that patients with NVAF on DOACs would need a more accurate definition of their optimal therapeutic window.

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Background Prothrombin time (PT) and activated partial thromboplastin time (APTT) have been proposed to measure the effect of oral anti-activated factor X (FXa) or anti-activated FII drugs, respectively. Aims To evaluate the relationships and responsiveness of PT and APTT versus direct oral anticoagulant (DOAC) concentrations measured with specific coagulation tests performed with different platforms in four Italian anticoagulation clinics. Methods Six hundred and thirty-five patients with atrial fibrillation participated in the study: 240 were receiving dabigatran, 264 were receiving rivaroxaban, and 131 were receiving apixaban. Blood was taken at trough and peak within the first month (15-25 days) of treatment. PT, APTT, diluted thrombin time (dTT) calibrated for dabigatran and anti-FXa calibrated for rivaroxaban or apixaban were determined. Results For dabigatran, the correlation between APTT and dTT ranged from r = 0.80 to r = 0.62. For rivaroxaban, the correlation between the anti-FXa assay and PT ranged from r = 0.91 to r = 0.73. For apixaban, the correlation between the anti-FXa assay and PT was lower than for the two other drugs (r = 0.81 to r = 0.54). Despite the above significant correlations, the responsiveness of PT or APTT was relatively poor. A discrepancy between global testing and DOAC plasma concentrations was shown in a considerable proportion of patients, depending on the platform and drug, with values ranging from 6% to 62%. Conclusions Overall, poor responsiveness of the screening tests to DOAC concentrations was observed. PT and APTT normal values cannot exclude DOAC anticoagulant activity, and PT or APTT prolongation is not always associated with DOAC anticoagulant effect as determined with specific tests.