Rationale
Recent systematic reviews have shown the limited evaluation of VTE RAMs to date and we have highlighted the challenge of obtaining robust primary data.8–10 However, it would be worth updating recent systematic reviews to avoid research waste and ensure that further research is based on the best currently available data. Decision-analytic modelling of the published evidence can also be used to estimate the cost-effectiveness of VTE RAMs for hospital inpatients. It can determine whether risk assessment has the potential to be cost-effective compared with thromboprophylaxis for all and, if so, what threshold of risk should be used for providing thromboprophylaxis and what trade-off between sensitivity and specificity would be optimal. It can, therefore, increase the insights available from the existing evidence and identify areas of uncertainty that require further research. This is particularly valuable when ethical considerations limit the design of primary research.
Given that the widespread use of VTE prophylaxis limits the potential to undertake prognostic accuracy studies of VTE RAMs, future primary research may need to evaluate the comparative effectiveness and cost-effectiveness of implementing alternative approaches to risk assessment. This research could involve individual patient or cluster randomised interventional trial designs, quasi-randomised methods or observational methods. These methods could all benefit from using an efficient design, in which routine data sources are used to measure VTE and bleeding outcomes, and potentially also to record or implement RAMs as part of an evaluation. Efficient methods could increase the available sample size for future primary research and support a study comparing different risk-assessment methods. This could increase the potential range of feasible study designs and the information generated by future primary research. However, research is required to determine whether efficient methods are feasible for comparative evaluation of VTE RAMs. Specifically:
- In order to be used in future research designs, routine data sources need to accurately record VTE and bleeding outcomes.
- Efficient methods for recording or implementing RAMs should build upon existing methods of delivering risk assessment within a hospital setting.
- Future research comparing RAMS would need to ensure that different patients (and different proportions of patients) received prophylaxis, otherwise any differences in outcome would be difficult to attribute to the RAM used.
Objectives
We aimed to evaluate the cost-effectiveness of VTE RAMs in hospital inpatients, determine the optimal approach to providing thromboprophylaxis and determine how changing the risk threshold for prophylaxis affects cost-effectiveness. We also sought to evaluate the potential performance of different RAMs in an NHS setting, assess the use of efficient methods to capture data on risk characteristics and to determine the accuracy of efficient methods to capture relevant outcomes in a future trial. Our specific objectives were as follows:
- Update recent systematic reviews to identify VTE RAMs for hospital inpatients and estimate prognostic accuracy.
- Undertake decision-analytic modelling to determine the cost-effectiveness of VTE risk assessment compared to thromboprophylaxis for all and thromboprophylaxis for none, specifically determining the risk threshold that optimises effectiveness (QALYs) and cost-effectiveness (i.e. maximises net benefit assuming willingness to pay according to NICE thresholds).
- Use the decision-analytic model to identify key areas of uncertainty and determine the value of gathering additional information to reduce uncertainty.
- Pilot the use of efficient methods alongside routine practice to determine the feasibility of a future implementation study of VTE risk assessment tools in hospital inpatients.
- Estimate key parameters for planning a future implementation study.
Objectives 1, 2 and 3 are addressed by workstream 1 (systematic review and economic modelling). Objectives 4 and 5 are addressed by workstream 2 (cohort study).