A decision model to estimate a risk threshold for venous thromboembolism prophylaxis in hospitalized medical patients

Risk of Venous Thromboembolism in Pediatric Patients with Surgically Treated Lower-Extremity Fractures: A Propensity-Matched Cohort Study

BACKGROUND

Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is a substantial cause of morbidity and mortality among hospitalized patients. Although rare in the general pediatric population, VTE remains a potential concern in hospitalized children, particularly those with lower-extremity (LE) fractures. With this study, we aimed to determine the risk of VTE in pediatric patients with surgically treated LE fractures through a retrospective, propensity-matched, cohort analysis.

METHODS

The TriNetX Research Network, encompassing data from >80 health-care organizations and >120 million patient records, was utilized for this retrospective cohort study comparing 3 age-based cohorts (children [age of <14 years], adolescents [age of 14 to 17 years], and adults [age of ≥18 years]) who underwent surgical treatment of LE fractures between January 1, 2003, and January 1, 2023.

RESULTS

A total of 634,880 patients with surgically treated LE fractures were included; 13.3% were children, 5.6% were adolescents, and 81.1% were adults. Propensity-score matching was used to compare VTE incidence across cohorts, resulting in 3 independent matched comparisons. Overall, the incidence of VTE (either DVT or PE) was 0.2% in children, 1.0% in adolescents, and 4.1% in adults. Adults had a significantly higher risk of developing DVT (risk ratio [RR]: 17.0; 95% confidence interval [CI]: 14.5 to 20.0) and PE (RR: 21.8; 95% CI: 17.0 to 28.1) compared with children. Similarly, adolescents had a higher risk of DVT (RR: 3.5; 95% CI: 2.7 to 4.4) and PE (RR: 3.1; 95% CI: 2.2 to 4.4) compared with children. The incidence of VTE varied by fracture location, with femoral and knee joint (incidence: 0.5% in children, 2.5% in adolescents) and pelvic and hip joint (incidence: 1.2% in children, 2.8% in adolescents) fractures presenting the highest risk across all age groups.

CONCLUSIONS

The incidence of VTE in a large cohort of pediatric patients undergoing surgical treatment of LE fractures was higher in adolescents than in children. These findings may warrant prophylactic VTE measures in adolescents undergoing surgical treatment of femoral or pelvic fractures.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

How Do Venous Thromboembolism Rates in Adolescents and Adults Compare After Arthroscopic Knee Surgery? A Propensity-Matched Study

BACKGROUND

Arthroscopic knee procedures such as meniscus and ACL repairs are cornerstone interventions in pediatric and sports orthopaedics. While venous thromboembolism (VTE), including pulmonary embolism (PE) and deep vein thrombosis (DVT), is a rare yet devastating complication in major joint surgeries, its association with minimally invasive procedures remains relatively unexplored. Emerging evidence shows rates of VTE in adolescent orthopaedic patients approaching that of adults, highlighting the need to further characterize the unique risk profile of this population. Therefore, this study aims to compare VTE rates, risk factors, and chemoprophylaxis use in adolescents versus adults undergoing arthroscopic knee procedures.

METHODS

A retrospective cohort study using the TriNetX Research Network identified 301,585 patients who underwent knee arthroscopy from January 2003 to January 2023, including 29,984 adolescents (aged 14 to 17) and 271,601 adults (aged 18 years or older). Propensity score matching based on sex and relevant comorbidities, including diabetes mellitus, tobacco use, oral contraceptive (OCP) use, and obesity yielded balanced cohorts of 29,984 each. Univariate logistic regression analysis was performed for preliminary assessment of the risk factors associated with VTE. P<0.01 was considered significant.

RESULTS

Adults had a higher 90-day incidence of DVT (1.3% vs. 0.8%) and PE (0.3% vs. 0.2%) than adolescents. Combined DVT/PE incidence was 1.5% in adults and 0.8% in adolescents (RR: 1.782). Univariate analysis showed OCP use (OR: 3.167), obesity (OR: 3.445), tobacco use (OR: 23.975), and diabetes (OR: 34.064) were significant VTE risk factors in adolescents; sex was not. Adults more frequently received postoperative chemoprophylaxis (24% vs. 20%, P<0.001), with aspirin being the most common agent (23% in adults vs. 19% in adolescents, P<0.001).

CONCLUSION

Adolescents undergoing knee arthroscopy have a lower risk of VTE compared with adults, with an incidence below 1%. Routine VTE prophylaxis may not be necessary for all adolescents but should be considered for those with significant risk factors, including diabetes, tobacco use, and obesity. Further research is warranted to refine prophylaxis guidelines in this population.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

Assessing Venous Thromboembolism Risk in Hip Arthroscopy: A Propensity-matched Comparison of Adolescents and Adults

BACKGROUND

Hip arthroscopy is a commonly performed procedure in adolescents with hip pathology. However, there is limited data on venous thromboembolism (VTE) events in this population, resulting in minimal guidance on appropriate VTE prophylaxis, with the bulk of current guidance extrapolated from the adult population. Therefore, this study aims to assess overall rates of VTE in the adolescent population as well as compare these rates to a matched cohort of adult patients undergoing hip arthroscopy.

METHODS

This retrospective cohort study drew data from the TriNetX platform between January 1, 2003 and March 1, 2024. Adolescent patients, ages 13 to 18, were matched to adult patients (19 and older) undergoing hip arthroscopy, accounting for sex, tobacco use, oral contraceptive use, diabetes mellitus, and overweight/obesity. Outcomes of interest were deep vein thrombosis (DVT) or pulmonary embolism (PE) within 90 days after the procedure. Overall rates were calculated and compared between cohorts. Statistical significance was set at P<0.01.

RESULTS

A total of 3655 patients were successfully matched with a mean age of 16 in the adolescent cohort and 35 in the adult cohort. The overall rates of DVT were similar between cohorts, at 1% for adolescent patients and 0.9% for adults (RR: 0.892; 95% CI: 0.559-1.423; P=0.63). All VTE events (combined DVT and PE) were also similar at 1.1% for adolescent patients and 1.0% in adults (RR: 0.925; 95% CI: 0.593-1.443; P=0.73).

CONCLUSION

This study found no significant difference in VTE between adolescent and adult patients undergoing hip arthroscopy. The overall rate of VTE was relatively high in adolescent patients, at 1.1%, suggesting additional attention to VTE and potential chemoprophylaxis may be warranted in select patients.

LEVEL OF EVIDENCE

Level III-case-control study or retrospective cohort study.

Risk of Venous Thromboembolism in Adolescents Undergoing Pelvic Osteotomy: Insights From a Propensity-matched Retrospective Cohort Study

BACKGROUND

Pelvic osteotomies are surgical procedures that are commonly performed in adolescents and young adults to improve stability or correct various deformities. Venous thromboembolism (VTE), including pulmonary embolism (PE) and deep vein thrombosis (DVT), are dreaded complications of any major procedure including pelvic osteotomies. Unlike adults, the incidence of DVT and need for prophylactic measures are not well understood in the adolescents. The purpose of this study is to understand the need for VTE prophylaxis in adolescents and determine if their risk profile aligns with adults, who have more established VTE prophylactic guidelines in place for these surgeries.

METHODS

This retrospective cohort study utilized data from the TriNetX Research Network, which includes records from over 80 healthcare organizations and more than 120 million patients. De-identified patient data from January 1, 2003, to March 1, 2024, were extracted using relevant ICD-9 and ICD-10 procedural codes. The study included 2 cohorts: patients aged 13 to 17 years (adolescents) and patients 18 years and older (adults) who underwent pelvic osteotomies. To control for confounding variables, propensity score matching was employed based on sex and relevant comorbidities, including diabetes mellitus, tobacco use, and overweight/obesity. Statistical significance was set at P <0.01.

RESULTS

A total of 2374 patients successfully matched in each cohort. Within 90 days following surgical intervention, adult patients had overall risks of 4.5%, 1.9%, and 5.9%, whereas adolescent patients had overall risks of 1.3%, 0.5%, and 1.4% for DVT (RR: 3.419), PE (RR: 4.182), and either DVT or PE (RR: 4.118), respectively.

CONCLUSIONS

This study examines the rate of VTE in a large cohort of adolescents undergoing pelvic osteotomies. Although we found the rates to be lower in adolescents compared with adults, the high absolute risk in adolescents-above 1%, the threshold established in the literature for considering prophylaxis-underscores the need for tailored risk stratification strategies and targeted thromboprophylaxis protocols for this population.

LEVELS OF EVIDENCE

Level III: case-control study or retrospective cohort study.

Fragility index for extended prophylaxis following abdominopelvic surgery: A methodological survey

BACKGROUND

Fragility Index (FI) is increasingly used to assess robustness of statistically significant p-values reported in randomized controlled trials (RCTs). FI represents the lowest number of non-events changed to events that would make study findings non-significant. This methodological survey was designed to assess the fragility of the evidence for extended VTEp following major abdominopelvic surgery.

METHODS

MEDLINE, Embase, and CENTRAL were searched from inception to November 2023. RCTs with parallel, double-armed, superiority design comparing extended VTEp for patients undergoing major abdominopelvic surgery to controls with at least one statistically significant dichotomous outcome were included. Walsh et al.'s method of calculating FI was utilized.

RESULTS

After review of 611 citations, 6 RCTs were identified with 12 statistically significant outcomes between groups. The mean number of patients randomized per RCT was 419 (SD 176). The median FI was 1.5 (range: 1-4). The number of patients lost to follow-up was greater than the FI for 10/12 (83.3 ​%) outcomes.

CONCLUSIONS

Statistically significant differences reported in RCTs evaluating extended VTEp following major abdominopelvic surgery are not robust.

Stakeholder-informed positivity thresholds for disease markers and risk scores: a methodological framework and an application in obstructive lung disease

OBJECTIVES

A positivity threshold is often applied to markers or predicted risks to guide disease management. These thresholds are often decided exclusively by clinical experts despite being sensitive to the preferences of patients and general public as ultimate stakeholders.

STUDY DESIGN AND SETTING

We propose an analytical framework for quantifying the net benefit (NB) of an evidence-based positivity threshold based on combining preference-sensitive (eg, how individuals weight benefits and harms of treatment) and preference-agnostic (eg, the magnitude of benefit and the risk of harm) parameters. We propose parsimonious choice experiments to elicit preference-sensitive parameters from stakeholders, and targeted evidence synthesis to quantify the value of preference-agnostic parameters. We apply this framework to maintenance of azithromycin therapy for chronic obstructive pulmonary disease using a discrete choice experiment to estimate preference weights for attribute level associated with treatment. We identify the positivity threshold on 12-month moderate or severe exacerbation risk that would maximize the NB of treatment in terms of severe exacerbations avoided.

RESULTS

In the case study, the prevention of moderate and severe exacerbations (benefits) and the risk of hearing loss and gastrointestinal symptoms (harms) emerged as important attributes. Four hundred seventy seven respondents completed the discrete choice experiment survey. Relative to each percent risk of severe exacerbation, preference weights for each percent risk of moderate exacerbation, hearing loss, and gastrointestinal symptoms were 0.395 (95% confidence interval [CI] 0.338-0.456), 1.180 (95% CI 1.071-1.201), and 0.253 (95% CI 0.207-0.299), respectively. The optimal threshold that maximized NB was to treat patients with a 12-month risk of moderate or severe exacerbations ≥12%.

CONCLUSION

The proposed methodology can be applied to many contexts where the objective is to devise positivity thresholds that need to incorporate stakeholder preferences. Applying this framework to chronic obstructive pulmonary disease pharmacotherapy resulted in a stakeholder-informed treatment threshold that was substantially lower than the implicit thresholds in contemporary guidelines.

What Constitutes High Risk for Venous Thromboembolism? Comparing Approaches to Determining an Appropriate Threshold

Background

Guidelines recommend pharmacological venous thromboembolism (VTE) prophylaxis only for high-risk patients, but the probability of VTE considered "high-risk" is not specified. Our objective was to define an appropriate probability threshold (or range) for VTE risk stratification and corresponding prophylaxis in medical inpatients.

Methods

Patients were adults admitted to any of 10 Cleveland Clinic Health System hospitals between December 2020 and August 2021 (N = 41,036). Hospital medicine physicians and internal medicine residents from included hospitals were surveyed between June and November 2023 (N = 214). We compared five approaches to determining a threshold: decision analysis, maximizing the sensitivity and specificity of a logistic regression model, deriving a probability from a point-based model, surveying physicians' understanding of VTE risk, and deriving a probability from physician behavior. For each approach, we determined the probability threshold above which a patient would be considered high-risk for VTE. We applied each threshold to the Cleveland Clinic VTE risk assessment model (CCM) and calculated the percentage of the 41,036 patients in our cohort who would be considered eligible for prophylaxis due to their high-risk status. We compared these hypothetical prophylaxis rates with physicians' observed prophylaxis rates.

Results

The different approaches yielded thresholds ranging from 0.3% to 5.4%, corresponding inversely with hypothetical prophylaxis rates of 0.2% to 75%. Multiple thresholds clustered between 0.52% to 0.55%, suggesting an average hypothetical prophylaxis rate of approximately 30%, whereas physicians' observed prophylaxis rates ranged from 48% to 76%.

Conclusions

Multiple approaches to determining a probability threshold for VTE prophylaxis converged to suggest an optimal threshold of approximately 0.5%. Other approaches yielded extreme thresholds that are unrealistic for clinical practice. Physicians prescribed prophylaxis much more frequently than the suggested rate of 30%, indicating opportunity to reduce unnecessary prophylaxis. To aid in these efforts, guidelines should explicitly quantify high-risk.

Evaluation of venous thromboembolism risk assessment models for hospital inpatients: the VTEAM evidence synthesis

Background

Pharmacological prophylaxis during hospital admission can reduce the risk of acquired blood clots (venous thromboembolism) but may cause complications, such as bleeding. Using a risk assessment model to predict the risk of blood clots could facilitate selection of patients for prophylaxis and optimise the balance of benefits, risks and costs.

Objectives

We aimed to identify validated risk assessment models and estimate their prognostic accuracy, evaluate the cost-effectiveness of different strategies for selecting hospitalised patients for prophylaxis, assess the feasibility of using efficient research methods and estimate key parameters for future research.

Design

We undertook a systematic review, decision-analytic modelling and observational cohort study conducted in accordance with Enhancing the QUAlity and Transparency Of health Research (EQUATOR) guidelines.

Setting

NHS hospitals, with primary data collection at four sites.

Participants

Medical and surgical hospital inpatients, excluding paediatric, critical care and pregnancy-related admissions.

Interventions

Prophylaxis for all patients, none and according to selected risk assessment models.

Main outcome measures

Model accuracy for predicting blood clots, lifetime costs and quality-adjusted life-years associated with alternative strategies, accuracy of efficient methods for identifying key outcomes and proportion of inpatients recommended prophylaxis using different models.

Results

We identified 24 validated risk assessment models, but low-quality heterogeneous data suggested weak accuracy for prediction of blood clots and generally high risk of bias in all studies. Decision-analytic modelling showed that pharmacological prophylaxis for all eligible is generally more cost-effective than model-based strategies for both medical and surgical inpatients, when valuing a quality-adjusted life-year at £20,000. The findings were more sensitive to uncertainties in the surgical population; strategies using risk assessment models were more cost-effective if the model was assumed to have a very high sensitivity, or the long-term risks of post-thrombotic complications were lower. Efficient methods using routine data did not accurately identify blood clots or bleeding events and several pre-specified feasibility criteria were not met. Theoretical prophylaxis rates across an inpatient cohort based on existing risk assessment models ranged from 13% to 91%.

Limitations

Existing studies may underestimate the accuracy of risk assessment models, leading to underestimation of their cost-effectiveness. The cost-effectiveness findings do not apply to patients with an increased risk of bleeding. Mechanical thromboprophylaxis options were excluded from the modelling. Primary data collection was predominately retrospective, risking case ascertainment bias.

Conclusions

Thromboprophylaxis for all patients appears to be generally more cost-effective than using a risk assessment model, in hospitalised patients at low risk of bleeding. To be cost-effective, any risk assessment model would need to be highly sensitive. Current evidence on risk assessment models is at high risk of bias and our findings should be interpreted in this context. We were unable to demonstrate the feasibility of using efficient methods to accurately detect relevant outcomes for future research.

Future work

Further research should evaluate routine prophylaxis strategies for all eligible hospitalised patients. Models that could accurately identify individuals at very low risk of blood clots (who could discontinue prophylaxis) warrant further evaluation.

Study registration

This study is registered as PROSPERO CRD42020165778 and Researchregistry5216.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR127454) and will be published in full in Health Technology Assessment; Vol. 28, No. 20. See the NIHR Funding and Awards website for further award information.

Effectiveness and cost effectiveness of pharmacological thromboprophylaxis for medical inpatients: decision analysis modelling study

Objective

To determine the balance of costs, risks, and benefits for different thromboprophylaxis strategies for medical patients during hospital admission.

Design

Decision analysis modelling study.

Setting

NHS hospitals in England.

Population

Eligible adult medical inpatients, excluding patients in critical care and pregnant women.

Interventions

Pharmacological thromboprophylaxis (low molecular weight heparin) for all medical inpatients, thromboprophylaxis for none, and thromboprophylaxis given to higher risk inpatients according to risk assessment models (Padua, Caprini, IMPROVE, Intermountain, Kucher, Geneva, and Rothberg) previously validated in medical cohorts.

Main outcome measures

Lifetime costs and quality adjusted life years (QALYs). Costs were assessed from the perspective of the NHS and Personal Social Services in England. Other outcomes assessed were incidence and treatment of venous thromboembolism, major bleeds including intracranial haemorrhage, chronic thromboembolic complications, and overall survival.

Results

Offering thromboprophylaxis to all medical inpatients had a high probability (>99%) of being the most cost effective strategy (at a threshold of £20 000 (€23 440; $25 270) per QALY) in the probabilistic sensitivity analysis, when applying performance data from the Padua risk assessment model, which was typical of that observed across several risk assessment models in a medical inpatient cohort. Thromboprophylaxis for all medical inpatients was estimated to result in 0.0552 additional QALYs (95% credible interval 0.0209 to 0.1111) while generating cost savings of £28.44 (-£47 to £105) compared with thromboprophylaxis for none. No other risk assessment model was more cost effective than thromboprophylaxis for all medical inpatients when assessed in deterministic analysis. Risk based thromboprophylaxis was found to have a high (76.6%) probability of being the most cost effective strategy only when assuming a risk assessment model with very high sensitivity is available (sensitivity 99.9% and specificity 23.7% v base case sensitivity 49.3% and specificity 73.0%).

Conclusions

Offering pharmacological thromboprophylaxis to all eligible medical inpatients appears to be the most cost effective strategy. To be cost effective, any risk assessment model would need to have a very high sensitivity resulting in widespread thromboprophylaxis in all patients except those at the very lowest risk, who could potentially avoid prophylactic anticoagulation during their hospital stay.

Generalizability of COBRA: A Parsimonious Perioperative Venous Thromboembolism Risk Assessment Model

INTRODUCTION

Standardized use of venous thromboembolism (VTE) risk assessment models (RAMs) in surgical patients has been limited, in part due to the cumbersome workflow addition required to use available models. The COBRA score-capturing cancer diagnosis, (old) age, body mass index, race, and American Society of Anesthesiologists Physical Status score-has been reported as a potentially automatable VTE RAM that circumvents the cumbersome workflow addition that most RAMs represent. We aimed to test the ability of the COBRA model to effectively risk-stratify patients across various populations.

METHODS

Patients were included from the 2014-2019 American College of Surgeons National Surgical Quality Improvement Program (NSQIP) Participant Use Data File for two hospitals, representing colorectal, endocrine, breast, transplant, plastic, and general surgery services. COBRA score was calculated for each patient using preoperative characteristics. We calculated negative predictive value (NPV) for VTE outcomes and compared the COBRA score to NSQIP's expected VTE rate for all patients, between the two hospitals, and between subspecialty service lines.

RESULTS

Of the 10,711 patients included, those with COBRA <4 (31%) had projected median VTE rate of 0.21% (interquartile range, 0.09-0.68%; mean, 0.54%). Patients with higher scores (69%) had median rate of 0.88% (0.26-2.07%; 1.46%); relative rate 2.7. The median projected VTE rates for patients identified as low risk were 0.21% and 0.16% and as high risk were 0.87% and 0.89% at hospitals one and 2, respectively. The median projected VTE rates for patients identified as low risk were 0.17%, 0.61%, and 0.08% and as high risk were 0.52%, 1.43%, and 0.18% among general, colorectal, and endocrine surgery patients, respectively. COBRA had NPV of 0.995 and sensitivity of 0.871 as compared to NPV 0.997 and sensitivity 0.857 of the NSQIP model.

CONCLUSIONS

The COBRA score is concordant with the traditional gold standard NSQIP VTE RAM and demonstrates interhospital and service-specific generalizability, although performance was limited in especially low-risk patients. The model adequately risk-stratifies surgical patients preoperatively, potentially providing clinical decision support for perioperative workflows.

Safety and efficacy of venous thromboembolism prophylaxis in patients with cirrhosis: A systematic review and meta-analysis

BACKGROUND & AIMS

Patients with cirrhosis are considered in a haemostatic balance, though weaker than in normal subjects. In these patients, however, the use of pharmacological prophylaxis for venous thromboembolism (VTE) remains controversial. Therefore, in this study, we aimed to assess the safety and efficacy of VTE prophylaxis in patients with cirrhosis.

METHODS

We conducted a systematic review of studies reporting the occurrence of bleeding and VTE events in patients with cirrhosis, and controls, undergoing VTE prophylaxis. Meta-regression analysis was conducted to further explore the determinants of heterogeneity in the study of the occurrence of either bleeding or VTE events.

RESULTS

In a total of 10 studies, including 5712 patients, of which 2330 undergoing VTE prophylaxis, bleeding (n = 5513) and VTE events occurred in 8.2% and 2.8% patients respectively. A total of 2963 and 3162 patients were included from low-risk of bias studies in bleeding and VTE analysis respectively: while administration of VTE prophylaxis did not seem to reduce VTE (OR = 1.07, CI 0.39-2.96, p = .89), importantly prophylaxis was not associated with increased bleeding risk (OR = 0.56, CI 0.20-1.59, p = .27). Meta-regression analysis showed that no parameter significantly influenced the heterogeneity of data regarding bleeding or VTE events.

CONCLUSIONS

In patients with cirrhosis, current evidence is insufficient to advise for or against the use of VTE prophylaxis, mainly due to lack of quality and homogeneity of available data. However, its use does not appear to be associated with a significant bleeding risk. Adequately designed studies are required to provide a measure of its overall utility.

Outcome of pharmacological thromboprophylaxis in hospitalized patients with cirrhosis - a systematic review and meta-analysis

BACKGROUND

Portal hypertension in cirrhosis brings about a complex interplay in the risks of bleeding and thrombosis. It is unclear whether hospitalized patients with cirrhosis need pharmacological prophylaxis for venous thromboembolism (VTE), as it may increase the risk of bleeding. We aimed to compare the outcome of hospitalized patients with cirrhosis with and without pharmacological thromboprophylaxis.

METHODS

A comprehensive search of three databases was conducted from inception to August 2022 for studies comparing the outcome of hospitalized patients with cirrhosis with and without pharmacological prophylaxis for VTE. Odds ratios (OR) with 95% confidence intervals (CIs) were calculated for the outcomes of VTE or bleeding.

RESULTS

Overall, 12 studies were included in the final analysis. The pooled incidence of VTE in patients with and without thromboprophylaxis was 1.9% (95% CI: 0.8-2.9) and 1.9% (95% CI: 0.9-2.9), respectively. The odds of VTE were comparable between the groups with OR 1.11 (95% CI: 0.76-1.62). The pooled incidence of bleeding events in patients with and without thromboprophylaxis was 6.7% (95% CI: 3.6-9.8) and 10.4% (95% CI: 6.6-14.1), respectively. There was no significant difference in the odds of overall bleeding (OR 0.68; 95% CI: 0.30-1.52) or major bleeding (OR 1.18; 95% CI: 0.55-2.56) between the groups. There was no significant difference in the relative effects on sensitivity analysis.

CONCLUSION

The present analysis could not demonstrate the benefit of pharmacological thromboprophylaxis in reducing in-hospital VTE in patients with cirrhosis. Future studies are required to assess the role of risk prediction models in hospitalized patients with cirrhosis.

A systematic approach to venous thromboembolism prevention: a focus on UK experience

Venous thromboembolism (VTE) remains a leading cause of preventable morbidity and mortality associated with hospitalization. Despite evidence that providing appropriate thromboprophylaxis to those at risk of VTE in hospital, recent data suggest that the delivery of thromboprophylaxis remains suboptimal across the globe, with a lack of standardization in approach to VTE prevention. This review considers the role of VTE risk assessment and interventions to improve the implementation of the VTE prevention pathway and highlights the systematic approach to VTE prevention adopted in England and its impact. Finally, the critical areas for further research and the emerging data presented during the 2022 ISTH annual congress in London, UK, are summarized.

Tailored Bayes: a risk modeling framework under unequal misclassification costs

Risk prediction models are a crucial tool in healthcare. Risk prediction models with a binary outcome (i.e., binary classification models) are often constructed using methodology which assumes the costs of different classification errors are equal. In many healthcare applications, this assumption is not valid, and the differences between misclassification costs can be quite large. For instance, in a diagnostic setting, the cost of misdiagnosing a person with a life-threatening disease as healthy may be larger than the cost of misdiagnosing a healthy person as a patient. In this article, we present Tailored Bayes (TB), a novel Bayesian inference framework which "tailors" model fitting to optimize predictive performance with respect to unbalanced misclassification costs. We use simulation studies to showcase when TB is expected to outperform standard Bayesian methods in the context of logistic regression. We then apply TB to three real-world applications, a cardiac surgery, a breast cancer prognostication task, and a breast cancer tumor classification task and demonstrate the improvement in predictive performance over standard methods.

Thromboprophylaxis for venous thromboembolism prevention in hospitalized patients with cirrhosis: Guidance from the SSC of the ISTH

Hospital-associated venous thromboembolism (HA-VTE) is a major cause of morbidity and mortality and is internationally recognized as a significant patient safety issue. While cirrhosis was traditionally considered to predispose to bleeding, these patients are also at an increased risk of VTE, with an associated increase in mortality. Hospitalization rates of patients with cirrhosis are increasing, and decisions regarding thromboprophylaxis are complex due to the uncertain balance between thrombosis and bleeding risk. This is further accentuated by derangements of hemostasis in patients with cirrhosis that are often considered contraindications to pharmacological thromboprophylaxis. Due to the strict inclusion and exclusion criteria of seminal studies of VTE risk assessment and thromboprophylaxis, there is limited data to guide decision making in this patient group. This guidance document reviews the incidence and risk factors for HA-VTE in patients with cirrhosis, outlines evidence to inform the use of thromboprophylaxis, and provides pragmatic recommendations on VTE prevention for hospitalized patients with cirrhosis. In brief, in hospitalized patients with cirrhosis: We suggest inclusion of portal vein thrombosis as a distinct clinically important endpoint for future studies. We recommend against the use of thrombocytopenia and/or prolongation of prothrombin time/international normalized ratio as absolute contraindications to anticoagulant thromboprophylaxis. We suggest anticoagulant thromboprophylaxis in line with local protocols and suggest low molecular weight heparin (LMWH) or fondaparinux over unfractionated heparin (UFH). In renal impairment, we suggest LMWH over UFH. For critically ill patients, we suggest case-by-case consideration of thromboprophylaxis. We recommend research to refine VTE risk stratification, and to establish the optimal dosing and duration of thromboprophylaxis.

Risk assessment models for venous thromboembolism in hospitalised adult patients: a systematic review

INTRODUCTION

Hospital-acquired thrombosis accounts for a large proportion of all venous thromboembolism (VTE), with significant morbidity and mortality. This subset of VTE can be reduced through accurate risk assessment and tailored pharmacological thromboprophylaxis. This systematic review aimed to determine the comparative accuracy of risk assessment models (RAMs) for predicting VTE in patients admitted to hospital.

METHODS

A systematic search was performed across five electronic databases (including MEDLINE, EMBASE and the Cochrane Library) from inception to February 2021. All primary validation studies were eligible if they examined the accuracy of a multivariable RAM (or scoring system) for predicting the risk of developing VTE in hospitalised inpatients. Two or more reviewers independently undertook study selection, data extraction and risk of bias assessments using the PROBAST (Prediction model Risk Of Bias ASsessment Tool) tool. We used narrative synthesis to summarise the findings.

RESULTS

Among 6355 records, we included 51 studies, comprising 24 unique validated RAMs. The majority of studies included hospital inpatients who required medical care (21 studies), were undergoing surgery (15 studies) or receiving care for trauma (4 studies). The most widely evaluated RAMs were the Caprini RAM (22 studies), Padua prediction score (16 studies), IMPROVE models (8 studies), the Geneva risk score (4 studies) and the Kucher score (4 studies). C-statistics varied markedly between studies and between models, with no one RAM performing obviously better than other models. Across all models, C-statistics were often weak (<0.7), sometimes good (0.7-0.8) and a few were excellent (>0.8). Similarly, estimates for sensitivity and specificity were highly variable. Sensitivity estimates ranged from 12.0% to 100% and specificity estimates ranged from 7.2% to 100%.

CONCLUSION

Available data suggest that RAMs have generally weak predictive accuracy for VTE. There is insufficient evidence and too much heterogeneity to recommend the use of any particular RAM.

PROSPERO REGISTRATION NUMBER

Steve Goodacre, Abdullah Pandor, Katie Sworn, Daniel Horner, Mark Clowes. A systematic review of venous thromboembolism RAMs for hospital inpatients. PROSPERO 2020 CRD42020165778. Available from https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=165778https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=165778.

Reassessment of venous thromboembolism and bleeding risk in medical patients receiving VTE prophylaxis

RATIONALE, AIMS, AND OBJECTIVES

The majority of hospitalized nonsurgical medical patients receive pharmacological prophylaxis for venous thromboembolism (VTE), and reassessment of changes in thrombosis and bleeding risk factors during hospital admission may represent an opportunity to discontinue unnecessary or unsafe therapy. The use of validated, clinically derived risk assessment models (RAMs) represents a shift towards an individualized, patient-centred approach to VTE prophylaxis. We are interested in using these tools to assess whether risk categories for VTE and bleeding change during admission and to assess whether such changes result in discontinuation of prophylaxis. Our primary objective was to determine whether VTE and bleed risk categories changed during the course of admission to warrant discontinuation of VTE prophylaxis, using the International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) VTE and Bleed RAMs, respectively. Secondary objectives were to determine the number of patients whose risk categorizations for VTE and bleeding warranted discontinuation of VTE prophylaxis and to survey whether prophylaxis was continued or discontinued.

METHODS

A retrospective review was undertaken for a cross-sectional, randomly selected sample of patients who received VTE prophylaxis while admitted to medical wards in a collection of regional hospitals.

RESULTS

Of the 351 medical records reviewed, only eight patients (2.3%) changed their VTE risk category and six (1.7%) changed their bleed risk category to warrant discontinuation of VTE prophylaxis. Ninety patients (26%) were at high risk of VTE and low risk of bleed throughout admission, warranting continued VTE prophylaxis. The majority of patients remained at low risk of VTE throughout admission but remained on VTE prophylaxis until discharge.

CONCLUSIONS

Risk categories for VTE and bleeding for medical patients did not appreciably change throughout hospital admission. Use of VTE RAMs at admission and prior to initiation of therapy should reduce unnecessary prophylaxis in the majority of medical patients who are at low risk of VTE.

Three myths about risk thresholds for prediction models

BACKGROUND

Clinical prediction models are useful in estimating a patient's risk of having a certain disease or experiencing an event in the future based on their current characteristics. Defining an appropriate risk threshold to recommend intervention is a key challenge in bringing a risk prediction model to clinical application; such risk thresholds are often defined in an ad hoc way. This is problematic because tacitly assumed costs of false positive and false negative classifications may not be clinically sensible. For example, when choosing the risk threshold that maximizes the proportion of patients correctly classified, false positives and false negatives are assumed equally costly. Furthermore, small to moderate sample sizes may lead to unstable optimal thresholds, which requires a particularly cautious interpretation of results.

MAIN TEXT

We discuss how three common myths about risk thresholds often lead to inappropriate risk stratification of patients. First, we point out the contexts of counseling and shared decision-making in which a continuous risk estimate is more useful than risk stratification. Second, we argue that threshold selection should reflect the consequences of the decisions made following risk stratification. Third, we emphasize that there is usually no universally optimal threshold but rather that a plausible risk threshold depends on the clinical context. Consequently, we recommend to present results for multiple risk thresholds when developing or validating a prediction model.

CONCLUSION

Bearing in mind these three considerations can avoid inappropriate allocation (and non-allocation) of interventions. Using discriminating and well-calibrated models will generate better clinical outcomes if context-dependent thresholds are used.

Venous thromboembolism incidence in the Ireland east hospital group: a retrospective 22-month observational study

OBJECTIVES

To determine the incidence of venous thromboembolism (VTE) and the incidence of hospital-acquired VTE (HA-VTE) arising within the population served by the Ireland East Hospital Group (IEHG).

DESIGN

/home/user/Documents/Sathish Kumar G/RFO/June/21-06-2019/bmjopen_iss_9_7_20190621_1/ A retrospective observational study was conducted using hospital discharge data obtained from the hospital inpatient enquiry data reporting system. In this system, VTE events recorded as 'primary diagnosis' represented the reason for initial hospital admission, whereas VTE recorded as a 'secondary diagnosis' occurred following admission and were therefore used as an approximation of HA-VTE. These data were used to estimate the overall incidence of VTE and the proportion of these events which were hospital-acquired.

SETTING

The IEHG is the largest hospital group in the Irish healthcare system and serves a population of over 1 million individuals.

PARTICIPANTS

Data were generated from records pertaining to the 2727 patient admission episodes where a diagnosis of VTE was made during the 22-month study period.

RESULTS

During the study period, 2727 VTE events were recorded within the IEHG (which serves a population of 1 036 279) corresponding to an incidence of 1.44 (95% CI 1.36 to 1.51) per 1000 per annum. 1273 (47%) of VTE events were recorded as secondary VTE. The incidence of VTE was highest among individuals over 85 years of age (16.03 per 1000;95% CI 12.81 to 19.26) and was more common following emergency hospital admission.

CONCLUSION

These data suggest that HA-VTE accounts for at least 47% of all VTE events arising within a hospital group serving a population of over 1 million individuals within the Ireland. Given that HA-VTE is a well-recognised source of (potentially preventable) hospital deaths, these findings provide a compelling argument for prioritising strategies directed at reducing the risk of VTE among hospital patients served by the IEHG and within the Ireland as a whole.

Cost-Effectiveness of Betrixaban Compared with Enoxaparin for Venous Thromboembolism Prophylaxis in Nonsurgical Patients with Acute Medical Illness in the United States

BACKGROUND

Studies show that the risk of venous thromboembolism (VTE) continues post-discharge in nonsurgical patients with acute medical illness. Betrixaban is the first anticoagulant approved in the United States (US) for VTE prophylaxis extending beyond hospitalization.

OBJECTIVE

The aim was to establish whether betrixaban for VTE prophylaxis in nonsurgical patients with acute medical illness at risk of VTE in the US is cost-effective compared with enoxaparin.

METHODS

A cost-effectiveness analysis was conducted, estimating the cost per quality-adjusted life-year (QALY) gained with betrixaban (35-42 days) compared with enoxaparin (6-14 days) from a US payer perspective over a lifetime horizon. A decision tree (DT) estimated primary VTE events, thrombotic events, and treatment complications in the first 3 months based on data from the phase III Acute Medically Ill VTE Prevention with Extended Duration Betrixaban study. A Markov model estimated recurrent events and long-term complication risks from published literature. EuroQoL-5 Dimensions utility data and costs inflated to 2017 US dollars (US$) were from published literature. Results were discounted at 3.0% per annum. Deterministic and probabilistic sensitivity analyses explored uncertainty.

RESULTS

Betrixaban dominated enoxaparin, with savings of US$784 and increased QALYs of 0.017 per patient. In addition, betrixaban dominated enoxaparin across all sensitivity analyses, but was most sensitive to utilities and DT probabilities. Furthermore, probabilistic sensitivity analysis found that betrixaban was more cost-effective than enoxaparin at all willingness-to-pay thresholds.

CONCLUSION

Betrixaban can be considered cost-effective for nonsurgical patients with acute medical illness at risk of VTE, requiring longer VTE prophylaxis from hospitalization through post-discharge.