External validation of the ADA score for predicting thrombosis among acutely ill hospitalized medical patients from the APEX Trial.

The ADA (Age-D-dimer-Albumin) score was developed to identify hospitalized patients at an increased risk for thrombosis in the coronavirus infectious disease-19 (COVID-19) setting. The study aimed to validate the ADA score for predicting thrombosis in a non-COVID-19 medically ill population from the APEX trial. The APEX trial was a multinational, randomized trial that evaluated the efficacy and safety of betrixaban vs. enoxaparin among acutely ill hospitalized patients at risk for venous thromboembolism. The study endpoints included the composite of arterial or venous thrombosis and its components. Metrics of model calibration and discrimination were computed for assessing the performance of the ADA score as compared to the IMPROVE score, a well-validated VTE risk assessment model. Among 7,119 medical inpatients, 209 (2.9%) had a thrombosis event up to 77 days of follow-up. The ADA score demonstrated good calibration for both arterial and venous thrombosis, whereas the IMPROVE score had adequate calibration for venous thrombosis (p > 0.05 from the Hosmer-Lemeshow test). For discriminating arterial and venous thrombosis, there was no significant difference between the ADA vs. IMPROVE score (c statistic = 0.620 [95% CI: 0.582 to 0.657] vs. 0.590 [95% CI: 0.556 to 0.624]; ∆ c statistic = 0.030 [95% CI: -0.022 to 0.081]; p = 0.255). Similarly, for discriminating arterial thrombosis, there was no significant difference between the ADA vs. IMPROVE score (c statistic = 0.582 [95% CI: 0.534 to 0.629] vs. 0.609 [95% CI: 0.564 to 0.653]; ∆ c statistic = -0.027 [95% CI: -0.091 to 0.036]; p = 0.397). For discriminating venous thrombosis, the ADA score was modestly superior to the IMPROVE score (c statistic = 0.664 [95% CI: 0.607 to 0.722] vs. 0.573 [95% CI: 0.521 to 0.624]; ∆ c statistic = 0.091 [95% CI: 0.011 to 0.172]; p = 0.026). The ADA score had a higher sensitivity (0.579 [95% CI: 0.512 to 0.646]; vs. 0.440 [95% CI: 0.373 to 0.507]) but lower specificity (0.625 [95% CI: 0.614 to 0.637] vs. 0.747 [95% CI: 0.737 to 0.758]) than the IMPROVE score for predicting thrombosis. Among acutely ill hospitalized medical patients enrolled in the APEX trial, the ADA score demonstrated good calibration but suboptimal discrimination for predicting thrombosis. The findings support the use of either the ADA or IMPROVE score for thrombosis risk assessment. The applicability of the ADA score to non-COVID-19 populations warrants further research.Clinical Trial Registration: http://www.clinicaltrials.gov . Unique identifier: NCT01583218.

Extended Thromboprophylaxis with Betrixaban in Acutely Ill Medical Patients.

BACKGROUND: Patients with acute medical illnesses are at prolonged risk for venous thrombosis. However, the appropriate duration of thromboprophylaxis remains unknown. METHODS: Patients who were hospitalized for acute medical illnesses were randomly assigned to receive subcutaneous enoxaparin (at a dose of 40 mg once daily) for 10±4 days plus oral betrixaban placebo for 35 to 42 days or subcutaneous enoxaparin placebo for 10±4 days plus oral betrixaban (at a dose of 80 mg once daily) for 35 to 42 days. We performed sequential analyses in three prespecified, progressively inclusive cohorts: patients with an elevated d-dimer level (cohort 1), patients with an elevated d-dimer level or an age of at least 75 years (cohort 2), and all the enrolled patients (overall population cohort). The statistical analysis plan specified that if the between-group difference in any analysis in this sequence was not significant, the other analyses would be considered exploratory. The primary efficacy outcome was a composite of asymptomatic proximal deep-vein thrombosis and symptomatic venous thromboembolism. The principal safety outcome was major bleeding. RESULTS: A total of 7513 patients underwent randomization. In cohort 1, the primary efficacy outcome occurred in 6.9% of patients receiving betrixaban and 8.5% receiving enoxaparin (relative risk in the betrixaban group, 0.81; 95% confidence interval [CI], 0.65 to 1.00; P=0.054). The rates were 5.6% and 7.1%, respectively (relative risk, 0.80; 95% CI, 0.66 to 0.98; P=0.03) in cohort 2 and 5.3% and 7.0% (relative risk, 0.76; 95% CI, 0.63 to 0.92; P=0.006) in the overall population. (The last two analyses were considered to be exploratory owing to the result in cohort 1.) In the overall population, major bleeding occurred in 0.7% of the betrixaban group and 0.6% of the enoxaparin group (relative risk, 1.19; 95% CI, 0.67 to 2.12; P=0.55). CONCLUSIONS: Among acutely ill medical patients with an elevated d-dimer level, there was no significant difference between extended-duration betrixaban and a standard regimen of enoxaparin in the prespecified primary efficacy outcome. However, prespecified exploratory analyses provided evidence suggesting a benefit for betrixaban in the two larger cohorts. (Funded by Portola Pharmaceuticals; APEX ClinicalTrials.gov number, NCT01583218.).

Inverse relationship of serum albumin to the risk of venous thromboembolism among acutely ill hospitalized patients: Analysis from the APEX trial.

Hypoalbuminemia is a common finding and independent predictor for unfavorable prognosis. The prognostic value of albumin measurement for short-term VTE prediction in hospitalized patients remains unclear. In the APEX trial (ClinicalTrials.gov identifier: NCT01583218), medical inpatients were randomized to receive either extended-duration betrixaban or shorter-duration enoxaparin and followed for 77 days. Baseline albumin concentrations were obtained in 7266 subjects with evaluable VTE endpoints. The association of baseline albumin to VTE was assessed, with adjustment for patient characteristics, thromboprophylaxis, and biomarkers for fibrinolysis and inflammation (ie, D-dimer and C-reactive protein [CRP]). VTE risk refinement was evaluated by incorporation of albumin to well-validated risk assessment models. A stepwise increase in the risk of VTE (P < .0001) was observed with lower levels of albumin. Patients at the bottom albumin quartile (<35 g/L) had a two-fold greater odds for developing VTE compared with the top quartile (≥42 g/L) (OR = 2.119 [95% CI, 1.592-2.820]; adjusted OR = 2.079 [1.485-2.911]). The odds for VTE increased by 1.368 (95% CI, 1.240-1.509) times per SD decrement of albumin (5.24 g/L). Compared with the propensity score-matched pairs of patients with albumin ≥35 g/L, patients with albumin <35 g/L had a greater risk of VTE (OR = 1.623 [1.260-2.090]; adjusted OR = 1.658 [1.209-2.272]). Albumin measurement also refined VTE risk discrimination and reclassification after inclusion in the risk assessment models. In conclusion, acutely ill hospitalized patients with low serum albumin had an increased VTE risk through 77 days. VTE risk assessment models for medical inpatients should consider incorporation of baseline albumin measurement.

Increased benefit of betrixaban among patients with a history of venous thromboembolism: a post-hoc analysis of the APEX trial.

Hospitalized acute medically ill patients with a history of venous thromboembolism (VTE) are at increased risk for recurrent VTE. We characterized the efficacy and safety of betrixaban for prevention of recurrent VTE in these high risk patients. The APEX trial randomized 7513 acutely ill hospitalized medical patients at risk for developing VTE to receive either betrixaban for 35-42 days or enoxaparin for 10 ± 4 days to prevent VTE. This exploratory post-hoc analysis assessed the efficacy and safety of betrixaban versus enoxaparin among subjects with and without prior VTE. Time-to-multiple symptomatic VTE events was also calculated. Approximately 8% of subjects in both arms had prior VTE, which was associated with a fourfold increase in adjusted risk of VTE [MV OR 4.03, 95% CI 3.06-5.30, p < 0.001]. Betrixaban reduced VTE compared with enoxaparin among subjects with prior VTE [32 (10.4%) vs. 55 (18.9%), RR 0.57, 95% CI 0.38-0.86, p = 0.006, ARR 8.5%, NNT 12] and without prior VTE [133 (3.9%) vs. 168 (4.9%), RR 0.79, 95% CI 0.64-0.99, p = 0.042, ARR 1.0%, NNT 100] (interaction p > 0.05). Additionally, four subjects in the enoxaparin arm and one subject in the betrixaban arm experienced a recurrent VTE. Compared with enoxaparin, betrixaban use was associated with reduction of recurrent VTE events through the active treatment period [36 vs. 57, HR 0.63, 95% CI 0.41-0.97, p = 0.045] and through the end of study [38 vs. 71, HR 0.54, 95% CI 0.36-0.81, p = 0.004]. Prior VTE is associated with a fourfold increase in the risk of VTE among hospitalized medically ill patients. Only 12 such patients would need to be treated with betrixaban versus enoxaparin to prevent an additional VTE endpoint. Betrixaban reduced not only the first but also all recurrent VTE events in a time-to-any-event analysis. TRIAL REGISTRATION: http://www.clinicaltrials.gov , Unique identifier: NCT01583218.

N-terminal pro-B-type natriuretic peptide and the risk of stroke among patients hospitalized with acute heart failure: an APEX trial substudy.

BACKGROUND: Among patients hospitalized with acute heart failure (HF), the prognostic value of N-terminal pro-B-type natriuretic peptide (NT-proBNP) in short-term stroke prediction remains unclear. METHODS: In the APEX trial, 7513 patients hospitalized for an acute medical illness were randomized to receive either extended-duration betrixaban (80 mg once daily for 35-42 days) or standard-of-care enoxaparin (40 mg once daily for 10 ± 4 days) for venous thromboprophylaxis. Baseline NT-proBNP concentrations were obtained in 3261 patients admitted for HF. Stroke events were adjudicated by an independent clinical events committee blinded to thromboprophylaxis allocation. The association of NT-proBNP level and other risk factors and biomarkers with stroke was assessed at 77 days after randomization. RESULTS: In univariate analysis, the risk of stroke at 77 days was associated with baseline NT-proBNP (HR 3.63 [95% CI 1.47-8.99]; P = 0.005), D-dimer (HR 2.73 [95% CI 1.03-7.20]; P = 0.043), and hsCRP (HR 3.03 [95% CI 1.36-6.75]; P = 0.007). In multivariable analysis adjusting for hsCRP and thromboprophylaxis, NT-proBNP was associated with the risk of stroke (adjusted HR 3.64 [95% CI 1.35-9.83]; P = 0.011). The interaction of NT-proBNP with the treatment effect was not significant (Pint = 0.30). CONCLUSIONS: Baseline NT-proBNP concentration was associated with short-term stroke among patients hospitalized with acute HF. Stroke risk assessment models should consider incorporation of NT-proBNP measurement.

Competing risk analysis in a large cardiovascular clinical trial: An APEX substudy.

Competing risk methods are time-to-event analyses that account for fatal and/or nonfatal events that may potentially alter or prevent a subject from experiencing the primary endpoint. Competing risk methods may provide a more accurate and less biased estimate of the incidence of an outcome but are rarely applied in cardiology trials. APEX investigated the efficacy of extended-duration betrixaban versus standard-duration enoxaparin to prevent a composite of symptomatic deep-vein thrombosis (proximal or distal), nonfatal pulmonary embolism, or venous thromboembolism (VTE)-related death in acute medically ill patients (n = 7513). The aim of the current analysis was to determine the efficacy of betrixaban vs standard-duration enoxaparin accounting for non-VTE-related deaths using the Fine and Gray method for competing risks. The proportion of non-VTE-related death was similar in both the betrixaban (133, 3.6%) and enoxaparin (136, 3.7%) arms, P = .85. Both the traditional Kaplan-Meier method and the Fine and Gray method accounting for non-VTE-related death as a competing risk showed equal reduction of VTE events when comparing betrixaban to enoxaparin (HR/SHR = 0.65, 95% 0.42-0.99, P = 0.046). Due to the similar proportion of non-VTE-related deaths in both treatment arms and the use of a univariate model, the Fine and Gray method provided identical results to the traditional Cox model. Using the Fine and Gray method in addition to the traditional Cox proportional hazards method can indicate whether the presence of a competing risk, which is dependent of the outcome, altered the risk estimate.

Venous thromboembolism risk in ischemic stroke patients receiving extended-duration enoxaparin prophylaxis: results from the EXCLAIM study.

BACKGROUND AND PURPOSE: The optimal duration of venous thromboembolism prophylaxis in acute stroke patients is unknown. This subanalysis of the Extended Prophylaxis for Venous ThromboEmbolism in Acutely Ill Medical Patients With Prolonged Immobilization (EXCLAIM) study investigated extended-duration thromboprophylaxis with enoxaparin, compared with placebo following standard-duration enoxaparin, in ischemic stroke patients. METHODS: Acutely ill medical patients with recently reduced mobility received open-label enoxaparin 40 mg for 10±4 days, and they were then randomized to double-blind enoxaparin 40 mg daily or placebo for further 28±4 days. Venous thromboembolism incidence (symptomatic/asymptomatic deep-vein thrombosis, symptomatic/fatal pulmonary embolism) up to day 28 after randomization and major bleeding rates up to 48 h after the last dose of study treatment were reported. RESULTS: In total, 389 of 5963 (6.5%) randomized patients had ischemic stroke: 198 received extended-duration prophylaxis and 191 placebo. Extended-duration prophylaxis reduced venous thromboembolism incidence versus placebo (2.4% versus 8.0%; absolute risk difference, -5.6%; 95% CI, -10.5% to -0.7%), but it was associated with an increase in major bleeding (1.5% versus 0% in enoxaparin and placebo groups; absolute risk difference, +1.5%; 95% CI, -0.2% to 3.2%). CONCLUSIONS: Extended-duration thromboprophylaxis with enoxaparin was associated with reduced venous thromboembolism risk and increased major bleeding in the subgroup of patients with ischemic stroke in the EXCLAIM study.

Inverse relationship between body mass index and risk of venous thromboembolism among medically ill hospitalized patients: Observations from the APEX trial.

Obesity is associated with cardiovascular complications such as diabetes and hypertension. However, obesity and high body mass index (BMI) can also be linked to improved clinical outcomes in certain patient populations. This counterintuitive observation is called the "obesity paradox." The effect of BMI on the risk of developing venous thromboembolism (VTE) in acutely ill medical patients remains unclear. In the Acute Medically Ill VTE Prevention with Extended Duration Betrixaban (APEX) trial, acutely ill hospitalized medical patients were randomized to receive either extended-duration betrixaban or shorter-duration enoxaparin and followed for 77 days. A total of 7372 patients with evaluable VTE endpoints had BMI measured at baseline. The association between BMI and VTE risk was assessed after adjusting for potential confounders. The multivariable adjusted ORs of VTE risk associated with BMI levels referencing the median BMI value (15, 18.5, 28.3 [reference], 35, 40, 45) were: 2.82 (95% CI, 1.32-6.04, [change from 28.3 to 15]), 1.85 (95% CI, 1.14-2.99, [change from 28.3 to 18.5]), 1.30 (95% CI, 1.04-1.63, [change from 28.3 to 35]), 1.13 (95% CI, 0.84-1.52, [change from 28.3 to 40]), and 0.91 (95% CI, 0.57-1.47, [change from 28.3 to 45]), respectively (p = 0.022). In conclusion, acutely ill hospitalized patients with lower BMI had a higher VTE risk through 77 days, which appears to be a manifestation of the BMI paradox.

Extended-duration venous thromboembolism prophylaxis in acutely ill medical patients with recently reduced mobility: a randomized trial.

BACKGROUND: Extended-duration low-molecular-weight heparin has been shown to prevent venous thromboembolism (VTE) in high-risk surgical patients. OBJECTIVE: To evaluate the efficacy and safety of extended-duration enoxaparin thromboprophylaxis in acutely ill medical patients. DESIGN: Randomized, parallel, placebo-controlled trial. Randomization was computer-generated. Allocation was centralized. Patients, caregivers, and outcome assessors were blinded to group assignment. (ClinicalTrials.gov registration number: NCT00077753) SETTING: 370 sites in 20 countries across North and South America, Europe, and Asia. PATIENTS: Acutely ill medical patients 40 years or older with recently reduced mobility (bed rest or sedentary without [level 1] or with [level 2] bathroom privileges). Eligibility criteria for patients with level 2 immobility were amended to include only those who had additional VTE risk factors (age >75 years, history of VTE, or active or previous cancer) after interim analyses suggested lower-than-expected VTE rates. INTERVENTION: Enoxaparin, 40 mg/d subcutaneously (2975 patients), or placebo (2988 patients), for 28 +/- 4 days after receiving open-label enoxaparin for an initial 10 +/- 4 days. MEASUREMENTS: Incidence of VTE up to day 28 and of major bleeding events up to 48 hours after the last study treatment dose. RESULTS: Extended-duration enoxaparin reduced VTE incidence compared with placebo (2.5% vs. 4%; absolute risk difference favoring enoxaparin, -1.53% [95.8% CI, -2.54% to -0.52%]). Enoxaparin increased major bleeding events (0.8% vs. 0.3%; absolute risk difference favoring placebo, 0.51% [95% CI, 0.12% to 0.89%]). The benefits of extended-duration enoxaparin seemed to be restricted to women, patients older than 75 years, and those with level 1 immobility. LIMITATION: Estimates of efficacy and safety for the overall trial population are difficult to interpret because of the change in eligibility criteria during the trial. CONCLUSION: Use of extended-duration enoxaparin reduces VTE more than it increases major bleeding events in acutely ill medical patients with level 1 immobility, those older than 75 years, and women. PRIMARY FUNDING SOURCE: Sanofi-aventis.

Gadolinium-enhanced magnetic resonance angiography for pulmonary embolism: a multicenter prospective study (PIOPED III).

BACKGROUND: The accuracy of gadolinium-enhanced magnetic resonance pulmonary angiography and magnetic resonance venography for diagnosing pulmonary embolism has not been determined conclusively. OBJECTIVE: To investigate performance characteristics of magnetic resonance angiography, with or without magnetic resonance venography, for diagnosing pulmonary embolism. DESIGN: Prospective, multicenter study from 10 April 2006 to 30 September 2008. SETTING: 7 hospitals and their emergency services. PATIENTS: 371 adults with diagnosed or excluded pulmonary embolism. MEASUREMENTS: Sensitivity, specificity, and likelihood ratios were measured by comparing independently read magnetic resonance imaging with the reference standard for diagnosing pulmonary embolism. Reference standard diagnosis or exclusion was made by using various tests, including computed tomographic angiography and venography, ventilation-perfusion lung scan, venous ultrasonography, d-dimer assay, and clinical assessment. RESULTS: Magnetic resonance angiography, averaged across centers, was technically inadequate in 25% of patients (92 of 371). The proportion of technically inadequate images ranged from 11% to 52% at various centers. Including patients with technically inadequate images, magnetic resonance angiography identified 57% (59 of 104) with pulmonary embolism. Technically adequate magnetic resonance angiography had a sensitivity of 78% and a specificity of 99%. Technically adequate magnetic resonance angiography and venography had a sensitivity of 92% and a specificity of 96%, but 52% of patients (194 of 370) had technically inadequate results. LIMITATION: A high proportion of patients with suspected embolism was not eligible or declined to participate. CONCLUSION: Magnetic resonance pulmonary angiography should be considered only at centers that routinely perform it well and only for patients for whom standard tests are contraindicated. Magnetic resonance pulmonary angiography and magnetic resonance venography combined have a higher sensitivity than magnetic resonance pulmonary angiography alone in patients with technically adequate images, but it is more difficult to obtain technically adequate images with the 2 procedures.

Machine learning to predict venous thrombosis in acutely ill medical patients.

BACKGROUND: The identification of acutely ill patients at high risk for venous thromboembolism (VTE) may be determined clinically or by use of integer-based scoring systems. These scores demonstrated modest performance in external data sets. OBJECTIVES: To evaluate the performance of machine learning models compared to the IMPROVE score. METHODS: The APEX trial randomized 7513 acutely medically ill patients to extended duration betrixaban vs. enoxaparin. Including 68 variables, a super learner model (ML) was built to predict VTE by combining estimates from 5 families of candidate models. A "reduced" model (rML) was also developed using 16 variables that were thought, a priori, to be associated with VTE. The IMPROVE score was calculated for each patient. Model performance was assessed by discrimination and calibration to predict a composite VTE end point. The frequency of predicted risks of VTE were plotted and divided into tertiles. VTE risks were compared across tertiles. RESULTS: The ML and rML algorithms outperformed the IMPROVE score in predicting VTE (c-statistic: 0.69, 0.68 and 0.59, respectively). The Hosmer-Lemeshow goodness-of-fit P-value was 0.06 for ML, 0.44 for rML, and <0.001 for the IMPROVE score. The observed event rate in the lowest tertile was 2.5%, 4.8% in tertile 2, and 11.4% in the highest tertile. Patients in the highest tertile of VTE risk had a 5-fold increase in odds of VTE compared to the lowest tertile. CONCLUSION: The super learner algorithms improved discrimination and calibration compared to the IMPROVE score for predicting VTE in acute medically ill patients.

Multidetector computed tomography for acute pulmonary embolism.

BACKGROUND: The accuracy of multidetector computed tomographic angiography (CTA) for the diagnosis of acute pulmonary embolism has not been determined conclusively. METHODS: The Prospective Investigation of Pulmonary Embolism Diagnosis II trial was a prospective, multicenter investigation of the accuracy of multidetector CTA alone and combined with venous-phase imaging (CTA-CTV) for the diagnosis of acute pulmonary embolism. We used a composite reference test to confirm or rule out the diagnosis of pulmonary embolism. RESULTS: Among 824 patients with a reference diagnosis and a completed CT study, CTA was inconclusive in 51 because of poor image quality. Excluding such inconclusive studies, the sensitivity of CTA was 83 percent and the specificity was 96 percent. Positive predictive values were 96 percent with a concordantly high or low probability on clinical assessment, 92 percent with an intermediate probability on clinical assessment, and nondiagnostic if clinical probability was discordant. CTA-CTV was inconclusive in 87 of 824 patients because the image quality of either CTA or CTV was poor. The sensitivity of CTA-CTV for pulmonary embolism was 90 percent, and specificity was 95 percent. CTA-CTV was also nondiagnostic with a discordant clinical probability. CONCLUSIONS: In patients with suspected pulmonary embolism, multidetector CTA-CTV has a higher diagnostic sensitivity than does CTA alone, with similar specificity. The predictive value of either CTA or CTA-CTV is high with a concordant clinical assessment, but additional testing is necessary when the clinical probability is inconsistent with the imaging results.

Reconstructed 4-chamber views compared with axial imaging for assessment of right ventricular enlargement on CT pulmonary angiograms.

PURPOSE: To test the hypothesis that right enlargement assessed from right ventricular/left ventricular (RV/LV) dimension ratios of computed tomographic (CT) angiograms are equivalent irrespective of whether measured on axial views or reconstructed 4-chamber views. METHODS: RV/LV dimension ratios were calculated from measurements on axial views, manually reconstructed 4-chamber views and computer generated reconstructed 4-chamber views of CT angiograms in 152 patients with PE. RESULTS: Paired readings of the axial view and manually reconstructed 4-chamber view showed agreement with RV/LV > or =1 or RV/LV <1 in 114 of 127 (89.8%). Paired readings also showed agreement in 119 of 127 (93.7%) with axial views and computer generated reconstructed 4-chamber views. The McNemar test showed no statistically significant difference between assessments of RV enlargement (RV/LV > or = 1) with any method. CONCLUSION: Right ventricular enlargement can be determined from axial views on CT angiograms, which are readily and immediately available, without obtaining 4-chamber reconstructed views.

State-of-the-art review: Assessing the safety profiles of new anticoagulants for major orthopedic surgery thromboprophylaxis.

BACKGROUND: The safety and efficacy of new anticoagulants are often initially tested for venous thromboembolism (VTE) prevention in patients undergoing major orthopedic surgery. Concern among surgeons about the risks for bleeding may result in suboptimal use of thrombophylaxis. OBJECTIVE: To evaluate the definitions used to define bleeding outcomes in studies of new anticoagulants and to examine the influence the definition has on the perceived bleeding risk of thromboprophylaxis. METHODS: The MedLine database was searched for phase III studies of new anticoagulants versus the standard comparator, enoxaparin, in patients undergoing major orthopedic surgery. RESULTS: The definitions for major bleeding outcomes varied widely both across and within clinical trial programs of new anticoagulants. Studies which did not include surgical site bleeding in their definition for major bleeding showed lower major bleeding rates in comparison to those that did include this outcome. Other factors that influenced the rate of major bleeding included the timing of prophylaxis initiation in relation to surgery and the dose of anticoagulant therapy. The wide range of definitions used for major bleeding made it difficult to compare bleeding risk among studies of new anticoagulants. CONCLUSIONS: The definitions of bleeding events that clinical trials of thromboprophylaxis use in their assessment of new anticoagulants strongly influences each drug's perceived safety profile and may underestimate bleeding risks. Clinical studies of new anticoagulants urgently need standardization of bleeding definitions to allow intertrial comparability and to ensure consistent reporting of clinically relevant outcomes.

Estimation of Acutely Ill Medical Patients at Venous Thromboembolism Risk Eligible for Extended Thromboprophylaxis Using APEX Criteria in US Hospitals.

Major medical illnesses place patients at risk of venous thromboembolism (VTE). Some risk factors including age ≥75 years or history of cancer place them at increased risk of VTE that extends for at least 5 to 6 weeks following hospital admission. Betrixaban thromboprophylaxis is now approved in the United States for this indication. We estimated the annual number of acutely ill medical patients at extended risk of VTE discharged from US hospital. Major medical illnesses (stroke, respiratory failure/chronic obstructive pulmonary disease, heart failure, pneumonia, other infections, and rheumatologic disorders) and 2 common risk factors for extended VTE risk, namely, age ≥75 years and history of cancer (active or past) were examined in 2014 US hospital discharges using the first 3 discharge diagnosis codes in the National Inpatient Sample (database of acute-care hospital discharges from the US Agency for Health Care Quality and Research). In 2014, there were 20.8 million discharges with potentially at risk of nonsurgical-related VTE. Overall, 7.2 million (35%) discharges corresponded to major medical illness that warranted thromboprophylaxis according to 2012 American College of Chest Physicians (ACCP) guideline. Among them, 2.79 million were aged ≥75 years and 1.36 million had a history of cancer (aged 40-74 years). Overall, 3.48 million discharges were at extended risk of VTE. Many medical inpatients at risk of VTE according to 2012 ACCP guideline might benefit from the awareness of continuing risk and some of these patients might benefit from extended thromboprophylaxis, depending on the risk of bleeding and comorbidities.

Net-clinical benefit of extended prophylaxis of venous thromboembolism with betrixaban in medically ill patients aged 80 or more.

BACKGROUND: Extended-duration thromboprophylaxis with betrixaban reduces the risk of venous thromboembolism (VTE) without increasing major bleeding rates in acutely ill medical patients as compared to standard duration enoxaparin. We aimed to assess the risk-benefit of betrixaban in patients aged ≥ 80 years enrolled in the APEX trial. METHODS: APEX was a randomized, double-blind trial in which patients hospitalized for acute medical illnesses received enoxaparin 40 mg qd for 10 ± 4 days or oral betrixaban 80 mg qd for 35 to 42 days. The primary efficacy outcome was VTE, the principal safety outcome was major bleeding. Net clinical benefit (NCB) was defined by the occurrence of VTE or major bleeding. RESULTS: Of 7513 patients enrolled in the APEX trial, 2781 (37%) were aged ≥ 80 years. In this subgroup, VTE or major bleeding occurred in 7.0% of betrixaban patients and in 8.4% of enoxaparin patients, for a relative risk in the NCB of 0.82 (95% confidence interval 0.62-1.10). The relative risk reduction obtained with betrixaban was similar between those aged ≥ 80 years and patients younger than 80 years (5.0% and 6.7%, respectively, NCB 0.75, 0.58-0.96, P = .024), with no significant interaction across age groups (P = .33). CONCLUSIONS: Event rates were higher in medically ill patients aged ≥ 80 years enrolled in the APEX study than in patients younger than 80 years. The predefined NCB was reduced with extended betrixaban therapy in both groups with no signs of age-related interactions. However, the primary efficacy endpoint was not achieved with betrixaban for patients 80 years of age or older.

Extended-duration betrixaban versus shorter-duration enoxaparin for venous thromboembolism prophylaxis in critically ill medical patients: an APEX trial substudy.

PURPOSE: To assess the efficacy and safety of betrixaban for venous thromboembolism (VTE) prophylaxis among critically ill patients. METHODS: The APEX trial randomized 7513 acutely ill hospitalized patients to betrixaban for 35-42 days or enoxaparin for 10 ± 4 days. Among those, 703 critically ill patients admitted to the intensive care unit were included in the analysis, and 547 patients who had no severe renal insufficiency or P-glycoprotein inhibitor use were included in the full-dose stratum. The risk of VTE, bleeding, net clinical benefit (composite of VTE and major bleeding), and mortality was compared at 35-42 days and at 77 days. RESULTS: At 35-42 days, extended betrixaban reduced the risk of VTE (4.27% vs 7.95%, P = 0.042) without causing excess major bleeding (1.14% vs 3.13%, P = 0.07). Both VTE (3.32% vs 8.33%, P = 0.013) and major bleeding (0.00% vs 3.26%, P = 0.003) were decreased in the full-dose stratum. Patients who received betrixaban had more non-major bleeding than enoxaparin (overall population: 2.56% vs 0.28%, P = 0.011; full-dose stratum: 3.32% vs 0.36%, P = 0.010). Mortality was similar at the end of study (overall population: 13.39% vs 16.19%, P = 0.30; full-dose stratum: 13.65% vs 16.30%, P = 0.39). CONCLUSIONS: Compared with shorter-duration enoxaparin, critically ill medical patients who received extended-duration betrixaban had fewer VTE without more major bleeding events. The benefit of betrixaban was driven by preventing asymptomatic thrombosis and offset by an elevated risk of non-major bleeding. The APEX trial did not stratify by intensive care unit admission and the present study included a highly selected population of critically ill patients. These hypothesis-generating findings need to be validated in future studies. CLINICAL TRIAL REGISTRATION: http://www.clinicaltrials.gov . Unique identifier: NCT01583218.

Characterization of Major and Clinically Relevant Non-Major Bleeds in the APEX Trial.

Background Among medically ill patients treated with thromboprophylaxis, betrixaban was not associated with an increase in major bleeding compared with enoxaparin, but an increase in clinically relevant non-major (CRNM) bleeding was observed. The aim of this analysis is to describe the severity and clinical consequences of major and CRNM bleeding in the APEX trial. Methods The APEX trial randomized 7,513 hospitalized acutely ill medical patients to receive either enoxaparin for 6 to 14 days or betrixaban for 35 to 42 days. Subjects receiving a concomitant strong p-glycoprotein inhibitor or with creatinine clearance <30 mL/min were administered a reduced dose of study drug. Results A total of 25 (0.7%) and 21 (0.6%) major bleeds occurred in the betrixaban and enoxaparin arms, respectively ( p = NS) and a total of 91 (2.5%) and 38 (1.0%) CRNM bleeds occurred in the betrixaban and enoxaparin arm ( p < 0.001), respectively. Most major bleeds were considered moderate or severe and most CRNM bleeds were considered mild and moderate ( p = NS). One fatal major bleed occurred in each treatment arm. Rates of major or CRNM bleeds resulting in new or prolonged hospitalization (major: 44.0 vs. 28.6%; CRNM: 12.1 vs. 21.1%) or study treatment interruption or cessation (major: 72.0 vs. 71.4%; CRNM: 71.3 vs. 68.4%) were similar between treatment arms ( p = NS). Conclusions In the APEX trial, CRNM bleeds were mild or moderate in nature and had less of a clinical impact than major bleeds. The severity and clinical sequela of bleeds in the betrixaban arm were comparable to those in the enoxaparin arm. Clinical Trial Registration URL: http://www.clinicaltrials.gov .; Unique identifier: NCT01583218.