How can anticoagulant thromboprophylaxis be personalised to reduce the risk of venous thromboembolism in acutely ill adult medical patients?

Background Venous thromboembolism (VTE), including pulmonary embolism and deep vein thrombosis, is a leading cause of morbidity and mortality in hospitalised patients. Over half of all VTE cases are provoked by hospitalisation, resulting in more than 32000 cases annually in the UK.

All patients admitted to hospital have their risk of VTE assessed at admission and patients at high risk of VTE are prescribed thromboprophylaxis, with low dose anticoagulants. However, thromboprophylaxis is not completely effective.

Approximately 50% of episodes of hospital-associated VTE occur despite provision of appropriate thromboprophylaxis, known as thromboprophylaxis failure.

Aims Identify risk factors associated with thromboprophylaxis failure in acutely ill adult medical patients at high risk of VTE. Explore patients' perspectives on thromboprophylaxis failure and understand acceptability of potential interventions.

Objectives Identify predictive risk factors of VTE in acutely ill adult medical patients receiving thromboprophylaxis from published research (study 1).

Assess whether the risk factors identified from study 1 correlate with thromboprophylaxis failure by developing and internally validating a predictive model, using retrospective data from two NHS hospital sites (study 2).

Explore participants perspectives, both those with and without a history of hospital-associated VTE, to inform future approaches to intensified VTE prevention practice (study 3).

Methods Study 1: A systematic review of published literature investigating individual risk factors associated with VTE in medical patients, following PRISMA guidance.

Risk factors whether identified through statistical analysis, individual studies or from current risk assessment models, will be extracted. Descriptive analysis will identify patient-identifiable risk factors for VTE.

Study 2: Internally validated predictive model which predicts thromboprophylaxis failure in medical patients using risk factors identified from study 1.

Demographics and risk factors will be extracted from the electronic patient record for 18000 patients using CogStack (information extraction platform) and risk factor validity assessed for a subset of data. Data from 2017-2018 will inform model development and 2019 data will validate the model. The final model will be compared to the current NHS VTE risk assessment tool.

Study 3: A discrete choice experiment will inform the acceptability of future potential interventions.

The experiment will involve participants with medical comorbidities who may or may not have experienced a hospital-associated VTE.

These participants will evaluate trade-offs and choose their preferred option from a selection of hypothetical thromboprophylaxis regimens.

To inform the discrete choice experiment, 15 one-to-one interviews will be conducted to explore current and alternative methods to prevent hospital-associated VTE, and bleeding concerns.

These will include people who have experienced a hospital-associated VTE and will be analysed using the Theoretical Framework of Acceptability.

Anticipated impact This research will provide insights into risk factors associated with thromboprophylaxis failure in medical patients and peoples' preferences for future interventions to reduce the risk of VTE. Key findings will be widely disseminated to stakeholders and the public.

Improving the identification of medical patients at risk of thromboprophylaxis failure will enable a personalised approach to improve VTE prevention.

This will lead to a decrease in hospital-associated VTE and most significantly, a reduction in morbidity and mortality associated with VTE.