Melissa Hamilton

Effectiveness and safety of apixaban versus warfarin in non-valvular atrial fibrillation patients in "real-world" clinical practice: a propensity-matched analysis of 76,940 patients

Summary The ARISTOTLE trial showed a risk reduction of stroke/systemic embolism (SE) and major bleeding in non-valvular atrial fibrillation (NVAF) patients treated with apixaban compared to warfarin. This retrospective study used four large US claims databases (MarketScan, PharMetrics, Optum, and Humana) of NVAF patients newly initiating apixaban or warfarin from January 1, 2013 to September 30, 2015. After 1:1 warfarin-apixaban propensity score matching (PSM) within each database, the resulting patient records were pooled. Kaplan-Meier curves and Cox proportional hazards models were used to estimate the cumulative incidence and hazard ratios (HRs) of stroke/SE and major bleeding (identified using the first listed diagnosis of inpatient claims) within one year of therapy initiation. The study included a total of 76,940 (38,470 warfarin and 38,470 apixaban) patients. Among the 38,470 matched pairs, 14,563 were from MarketScan, 7,683 were from PharMetrics, 7,894 were from Optum, and 8,330 were from Humana. Baseline characteristics were balanced between the two cohorts with a mean (standard deviation [SD]) age of 71 (12) years and a mean (SD) CHA 2 DS 2 -VASc score of 3.2 (1.7). Apixaban initiators had a significantly lower risk of stroke/SE (HR: 0.67, 95 % CI: 0.59–0.76) and major bleeding (HR: 0.60, 95 % CI: 0.54–0.65) than warfarin initiators. Different types of stroke/SE and major bleeding – including ischaemic stroke, haemorrhagic stroke, SE, intracranial haemorrhage, gastrointestinal bleeding, and other major bleeding – were all significantly lower for apixaban compared to warfarin treatment. Subgroup analyses (apixaban dosage, age strata, CHA 2 DS 2 -VASc or HAS-BLED score strata, or dataset source) all show consistently lower risks of stroke/SE and major bleeding associated with apixaban as compared to warfarin treatment. This is the largest “real-world” study on apixaban effectiveness and safety to date, showing that apixaban initiation was associated with significant risk reductions in stroke/SE and major bleeding compared to warfarin initiation after PSM. These benefits were consistent across various high-risk subgroups and both the standard-and low-dose apixaban dose regimens. Note: The review process for this manuscript was fully handled by Christian Weber, Editor in Chief. Supplementary Material to this article is available online at www.thrombosis-online.com .

Comparison of costs and discharge outcomes for patients hospitalized for ischemic or hemorrhagic stroke with or without atrial fibrillation in the United States.

This retrospective analysis investigated the impact of baseline clinical characteristics, including atrial fibrillation (AF), on hospital discharge status (to home or continuing care), mortality, length of hospital stay, and treatment costs in patients hospitalized for stroke. The analysis included adult patients hospitalized with a primary diagnosis of ischemic or hemorrhagic stroke between January 2006 and June 2011 from the premier alliance database, a large nationally representative database of inpatient health records. Patients included in the analysis were categorized as with or without AF, based on the presence or absence of a secondary listed diagnosis of AF. Irrespective of stroke type (ischemic or hemorrhagic), AF was associated with an increased risk of mortality during the index hospitalization event, as well as a higher probability of discharge to a continuing care facility, longer duration of stay, and higher treatment costs. In patients hospitalized for a stroke event, AF appears to be an independent risk factor of in-hospital mortality, discharge to continuing care, length of hospital stay, and increased treatment costs.

Risk of major bleeding in patients with non-valvular atrial fibrillation treated with oral anticoagulants: a systematic review of real-world observational studies

Abstract Objective: To conduct a systematic review of real-world (RWD) studies comparing the risk of major bleeding (MB) among patients with non-valvular atrial fibrillation (NVAF) on direct oral anticoagulants (DOACs) or warfarin. Methods: MEDLINE, Embase, NHS-EED, and EconLit were searched for RWD studies published between January 2003 and November 2016 comparing MB risk among DOACs and warfarin. Proceedings of clinical conferences from 2012 to 2016 were reviewed. Results: A total of 4218 citations were identified, 26 of which met eligibility criteria. Most studies were retrospective analyses of administrative claims databases and patient registries (n = 23 of 26); about half were based in the United States (n = 15). Apixaban showed a significantly lower risk of MB versus warfarin in all eight included studies. MB risk was either significantly lower (n = 9 of 16) or not significantly different (n = 7 of 16) between dabigatran and warfarin; there was no significant difference between rivaroxaban and warfarin in all seven included studies. The risk was significantly lower with apixaban versus rivaroxaban (n = 7 of 7) but not significantly different from dabigatran (n = 6 of 7). MB risk was significantly lower (n = 3 of 4) or not significantly different (n = 1 of 4) with dabigatran versus rivaroxaban. No evidence was identified for edoxaban. Conclusion: DOACs were associated with similar or lower risks of MB versus warfarin. A lower MB risk was consistently observed for apixaban, but less consistently for dabigatran; MB risk was similar between rivaroxaban and warfarin. Among DOACs, the risk of MB with apixaban was consistently lower than with rivaroxaban, but similar to dabigatran.

Venous thromboembolism prophylaxis and clinical consequences in medically ill patients.

The objective of this study was to examine venous thromboembolism (VTE) prophylaxis use, risk reduction, and readmission in medically ill patients during hospitalization and after discharge. This 5-year retrospective study linked outpatient files from MarketScan Commercial and Medicare Supplemental databases. Patients were categorized into prophylaxis and non-prophylaxis groups based on guideline-recommended anticoagulant use from the index date to 180 days posthospital discharge and before the first VTE event date. Outcome variables were VTE events and rehospitalization. Risk adjustment was conducted within the prophylaxis group and between the prophylaxis and non-prophylaxis groups using propensity score matching. Among 4467 patients, 28.99% of the patients (n = 1295) were admitted with cancer, 18.03% (n = 805) with pneumonia, 14.06% (n = 628) with heart failure, 11.06% (n = 494) with stroke, 11.11% (n = 496) with sepsis, 8.08% (n = 361) with infectious diseases, 5.6% (n = 250) with severe respiratory disorders, 1.81% (n = 81) with inflammatory bowel disease, 1.05% (n = 47) with obesity, 0.20% (n = 9) with neurologic disorders, and 0.02% (n = 1) with acute rheumatic fever. Among those with 180-day continuous enrollment after the index date (n = 3511), 51.81% (n = 1819) received anticoagulant therapy only, 2.48% (n = 87) received mechanical compression treatment only (stocking or pneumatic compression), and 4.41% (n = 155) received both during hospitalization. Anticoagulant therapy rates ranged from 88.64% (obesity) to 32.39% (inflammatory bowel disease). Among anticoagulant therapy patients, 740 patients (40.68%) received low–molecular weight heparin only and 806 patients (44.31%) received unfractionated heparin. After risk adjustment, compared with patients without VTE prophylaxis, anticoagulant prophylaxis patients had lower VTE (3.62% vs. 4.27%, P < 0.04) and readmission rates (24.22% vs. 27.95%, P < 0.02) during the 6 months post-index hospital admission. In conclusion anticoagulant prophylaxis is underutilized and is associated with reduced VTE risk and a decrease in rehospitalizations for medically ill patients.

Cost-effectiveness of Apixaban Versus Other Oral Anticoagulants for the Initial Treatment of Venous Thromboembolism and Prevention of Recurrence

PURPOSE To assess the cost-effectiveness of apixaban versus rivaroxaban, low-molecular-weight heparin (LMWH)/dabigatran, and LMWH/vitamin K antagonist (VKA) for the initial treatment and prevention of recurrent thromboembolic events in patients with venous thromboembolism (VTE). METHODS A Markov model was developed to evaluate the pharmacoeconomic effect of 6 months of treatment with apixaban versus other anticoagulants over a lifetime horizon. Network meta-analyses were conducted using the results of the Apixaban after the Initial Management of Pulmonary Embolism and Deep Vein Thrombosis with First-Line Therapy (AMPLIFY), EINSTEIN-pooled, and RE-COVER I and II trials for the following end points: recurrent VTE, major bleeds, clinically relevant non-major bleeds, and treatment discontinuations. The analysis was conducted from the perspective of the United Kingdom National Health Service. The outcomes evaluated were the number of events avoided in a 1000-patient cohort, total costs, life years, quality-adjusted life years (QALYs), and cost per QALY gained over a patients lifetime. FINDINGS Treatment for 6 months with apixaban was projected to result in fewer recurrent VTE and bleeding events in comparison to rivaroxaban, LMWH/dabigatran, and LMWH/VKA. Apixaban was cost-effective compared with LMWH/VKA at an incremental cost-effectiveness ratio of £2520 per QALY gained and was a dominant (ie, lower costs and higher QALYs) alternative to either rivaroxaban or LMWH/dabigatran. Sensitivity analysis indicated that results were robust over a wide range of inputs. IMPLICATIONS The assessment of the effects and costs of apixaban in this study predicted that apixaban is a dominant alternative to rivaroxaban and LMWH/dabigatran and a cost-effective alternative to LMWH/VKA for 6 months of treatment of VTE and the prevention of recurrence.

Outcomes associated with warfarin time in therapeutic range among US veterans with nonvalvular atrial fibrillation.

Abstract Background: Poor quality of warfarin control (time in therapeutic range [TTR] < 65%) can lead to increased risk of adverse events. The objective of this study was to examine the overall quality of international normalized ratio (INR) control and the association of TTR with clinical outcomes including stroke, major bleeding, and all-cause mortality among US warfarin users. Methods and results: This retrospective observational cohort study utilized the US Veterans Affairs electronic medical records database (VA EMR). Patients with NVAF who newly initiated warfarin from 1 January 2005 to 31 December 2015 were grouped into two cohorts based on TTR <65% or ≥65%. TTR was computed from INR test results. Clinical outcomes assessed were stroke/systemic embolism (SE), hemorrhagic stroke, ischemic stroke, and major bleeding, defined based on hospitalization with those conditions as primary diagnosis, as well as all-cause mortality. Patients were followed from warfarin initiation to the first occurrence of an outcome or censoring. Propensity score weighted time-varying Cox regression was used to evaluate the risk of the clinical events. A total of 127,385 NVAF patients with mean TTR of 51% were included. TTR <65% was observed in 65% of patients. Mean CHA2DS2-VASC score (SD) was 2.9 (1.5) in the low TTR cohort and 2.7 (1.4) in the high TTR cohort. Patients with TTR <65% had a higher risk for any stroke/SE (HR: 1.57; 95% CI: 1.41–1.75), major bleeding (HR: 2.78; 95% CI: 2.55–3.03) and all-cause mortality (HR: 1.73; 95% CI: 1.67–1.79). Conclusions: The observed quality of warfarin control in VA EMR suggests room for improvement given the association with elevated risk of adverse clinical outcomes.

Ischemic Stroke in Nonvalvular Atrial Fibrillation at Warfarin Initiation: Assessment via a Large Insurance Database

Background and Purpose— Stroke risk may increase shortly after warfarin initiation in nonvalvular atrial fibrillation patients. Because of the brief period and limited number of events, large samples are needed to study this effect. We compared 30-day rates of ischemic stroke between nonvalvular atrial fibrillation patients initiating warfarin to nonwarfarin comparators using an insurance claims database. Methods— We identified nonvalvular atrial fibrillation patients via 1 inpatient/2 outpatient diagnosis claims from the MarketScan database, January 1, 2009, to December 31, 2010. We studied patients initiating warfarin using prescription claims and 1:1 matched 22 669 initiators to comparators based on age, sex, diagnosis date, and warfarin propensity score. Follow-up began on initiation date; patients were censored at discontinuation/switch of therapy, disenrollment, or end of the study. The median follow-up was 415 days. Cox regression was used to study differences in ischemic stroke risks between warfarin initiators and comparators while controlling for important prognostic factors. Results— Warfarin initiators were generally similar to comparators in clinical features but had higher CHADS2 scores (1.26 versus 1.19). The first 30-day ischemic stroke rate was higher among warfarin initiators than comparators (1.47%/y (27/1836) versus 0.98%/y (18/1837); P=0.18) but lower subsequently (0.81%/y [134/16 543] versus 1.09%/y [406/37 248]; P=0.002). Multivariable regression confirmed a significant interaction between follow-up and warfarin use with the adjusted hazard ratios (95% confidence intervals) for warfarin/comparator as 1.46 (0.80–2.65) in the first 30 days and 0.70 (0.57–0.85) afterward. Conclusions— Warfarin effect was qualitatively different in the first 30 days after initiation than subsequently. This is consistent with a modest increase in stroke risk occurring briefly after starting warfarin.

Effectiveness and Safety of Apixaban versus Warfarin as Outpatient Treatment of Venous Thromboembolism in U.S. Clinical Practice

In the AMPLIFY clinical trial, apixaban was non-inferior to warfarin plus subcutaneous enoxaparin bridge therapy in the treatment of acute venous thromboembolism (VTE) and was associated with significantly less bleeding. This study evaluated their comparative effectiveness and safety in routine clinical practice. A matched-cohort design and data from four U.S. private health care claims databases were employed. Study population comprised patients who initiated outpatient treatment with apixaban versus warfarin (plus parenteral anticoagulant bridge therapy) within 30 days of their initial VTE episode; apixaban and warfarin patients were matched on age, characteristics of VTE episode, study database and propensity score. Major bleeding, clinically relevant non-major (CRNM) bleeding and recurrent VTE during the 180-day (maximum) follow-up period were compared using shared frailty models. During mean follow-up of 143 days among apixaban patients ( n  = 17,878) and 152 days among warfarin patients ( n  = 17,878), incidence proportions for apixaban versus warfarin, respectively, were 1.7% versus 2.3% for major bleeding, 7.0% versus 9.4% for CRNM bleeding and 2.3% versus 2.9% for recurrent VTE. In shared frailty models, risks of major bleeding (hazard ratio [HR] = 0.75, 95% confidence interval [CI] = 0.64–0.87), CRNM bleeding (HR = 0.77, 95% CI = 0.71–0.83) and recurrent VTE (HR = 0.80, 95% CI = 0.70–0.91) were lower for apixaban versus warfarin. In this large-scale evaluation of VTE patients receiving outpatient treatment with apixaban or warfarin in U.S. clinical practice, risks of major bleeding, CRNM bleeding and recurrent VTE were significantly lower among patients who received apixaban.

Correction: Comparison of the Non-VKA Oral Anticoagulants Apixaban, Dabigatran, and Rivaroxaban in the Extended Treatment and Prevention of Venous Thromboembolism: Systematic Review and Network Meta-Analysis.

[This corrects the article DOI: 10.1371/journal.pone.0160064.].

Effectiveness and Safety of Anticoagulants in Adults with Non-valvular Atrial Fibrillation and Concomitant Coronary/Peripheral Artery Disease

BACKGROUND Direct oral anticoagulants (DOAC) are at least non-inferior to warfarin in efficacy and safety among patients with nonvalvular atrial fibrillation. Limited evidence is available regarding outcomes for nonvalvular atrial fibrillation patients with coronary/peripheral artery disease. METHODS Non-valvular atrial fibrillation patients aged ≥65 years diagnosed with coronary/peripheral artery disease in the US Medicare population, newly initiating DOACs (apixaban, rivaroxaban, dabigatran) or warfarin were selected from January 1, 2013 to September 30, 2015. Propensity score matching was used to compare DOACs vs warfarin. Cox proportional hazards models were used to estimate the risk of stroke/systemic embolism, major bleeding, and composite of stroke/myocardial infarction/all-cause mortality. RESULTS There were 15,527 apixaban-warfarin, 6,962 dabigatran-warfarin, and 25,903 rivaroxaban-warfarin-matched pairs, with a mean follow-up of 5-6 months. Compared with warfarin, apixaban was associated with lower rates of stroke/systemic embolism (hazard ratio [HR] 0.48; 95% confidence interval [CI], 0.37-0.62), major bleeding (HR 0.66; 95% CI, 0.58-0.75), and stroke/myocardial infarction/all-cause mortality (HR 0.63; 95% CI, 0.58-0.69); dabigatran and rivaroxaban were associated with lower rates of stroke/myocardial infarction/all-cause mortality (HR 0.79; 95% CI, 0.70-0.90 and HR 0.87; 95% CI, 0.81-0.92, respectively). Rivaroxaban was associated with a lower rate of stroke/systemic embolism (HR 0.72; 95% CI, 0.60-0.89) and a higher rate of major bleeding (HR 1.14; 95% CI, 1.05-1.23) vs warfarin. CONCLUSIONS All DOACs were associated with lower stroke/myocardial infarction/all-cause mortality rates compared with warfarin; differences were observed in rates of stroke/systemic embolism and major bleeding. Findings from this observational analysis provide important insights about oral anticoagulation therapy among non-valvular atrial fibrillation patients with coronary/peripheral artery disease and may help physicians in the decision-making process when treating this high-risk group of patients.