PB1361 - Comparing the proportion of medical and surgical hospital inpatients requiring pharmacological thromboprophylaxis using different risk assessment models: an observational cohort study

Background: Risk Assessment Models (RAMs) are used at the point of hospital admission to quantify the individual risk of venous thromboembolism and guide prescribing of pharmacological prophylaxis. We recently conducted a systematic review describing 24 unique RAMs, with little evidence of comparative impact.

Aims: We sought to compare proportional recommendations for pharmacological thromboprophylaxis using six commonly applied RAMs alongside the UK Department of Health VTE risk assessment tool. Our main aim was to objectively characterise potential variation in prescribing.

Methods: A single centre observational cohort study. We identified a consecutive cohort of adult medical and surgical patients requiring hospitalisation during the calendar year 2019. We excluded patients requiring critical care admission, anticoagulation and pregnant/post-partum patients. We extracted initial clinical data using hospital admission records and VTE risk assessments completed prospectively by clinical teams using a structured note within the electronic healthcare record. We identified additional variables apriori to enable further completion of 6 prespecified RAMs; research assistants then undertook case note review and extracted data points necessary to facilitate retrospective completion.
We considered a sample of 250 patients to be sufficient to provide estimates of prescribing with a confidence interval range approaching 10%.

Results: We analysed 543 hospital episodes with VTE risk assessment performed. 289 episodes met exclusion criteria, leaving 254 episodes suitable for data extraction and comparative analysis. Overall recommendations for prescribing varied substantially between RAMs, ranging from 10% for the IMPROVE associative score to 91% for the Department of Health VTE risk assessment tool. Variation persisted throughout medical (11 to 92%) and surgical subgroups (9 to 88%).

Conclusion(s): Existing VTE RAMs produce highly variable rates of recommended pharmacological prophylaxis, when applied to a cohort of medical and surgical inpatients. The national UK Department of Health VTE RAM conferred significantly higher rates of prescribing than any other method.