PB1324 - Evaluating routine data sources and efficient methods to determine the incidence of venous thromboembolism and major bleeding in unselected medical and surgical inpatients.

Background: The accuracy of clinical outcome data is key to any future study of tailored thromboprophylaxis in hospitalised inpatients. However, any such study will require a large sample size.

Aims: We sought to evaluate the use of efficient methods to determine the feasibility of a data enabled implementation study of VTE risk assessment models. Our aim was to compare the accuracy of available coding (ICD10) and local registry data to determine key VTE and bleeding outcomes, against case note review by trained research assistants.

Methods: A multi-centre observational, cohort study with prespecified feasibility criteria conducted at four NHS sites.

We identified a consecutive cohort of general medical and surgical patients requiring hospitalisation during the calendar year 2019, then scrambled patient episodes into random batches to mitigate known and unknown confounders.

Research assistants subsequently undertook retrospective case note review for each patient episode through electronic health records, in sequential batches. We extracted data on the subsequent diagnosis of hospital acquired thrombosis (HAT) and major bleeding events as per internationally agreed definitions, up to 90 days following discharge. We then collated multiple routine outcome data sources for each patient episode and compared them to a reference standard diagnosis of case note review.

Results: 2115 patients were analysed with an original hospital admission occurring in the calendar year 2019. Of these, 107 patient episodes were ineligible, leaving 2008 episodes for analysis.

The sensitivity was 62% (95% CI 54% to 69%) for the use of coding data to detect HAT events and 81% (95% CI 75% to 87%) for local registry entries. The sensitivity of coding to detect major bleeding events was 38% (95% CI 27% to 50%).

Conclusion(s): In this multicentre cohort study, efficient data methods used to identify HAT and major bleeding events performed poorly when compared to direct case note review by trained research staff.