Cost-effectiveness analysis of doctor-pharmacist collaborative prescribing for venous thromboembolism in high risk surgical patients

Background: Current evidence to support cost effectiveness of doctor-pharmacist collaborative prescribing is limited. Our aim was to evaluate inpatient prescribing of venous thromboembolism (VTE) prophylaxis by a pharmacist in an elective surgery pre-admission clinic against usual care, to measure any benefits in cost to the healthcare system and quality adjusted life years (QALYs) of patients. Method: A decision tree model was developed to assess cost effectiveness of pharmacist prescribing compared with usual care for VTE prophylaxis in high risk surgical patients. Data from the literature was used to inform decision-tree probabilities, utility, and cost outcomes. In the intervention arm, a pharmacist prescribed patient's regular medications, documented a VTE risk assessment and prescribed VTE prophylaxis. In the usual care arm, resident medical officers were responsible for prescribing regular medications, and for risk assessment and prescribing of VTE prophylaxis. The base scenario assessed the cost effectiveness of a pre-existing pre-admission clinic pharmacy service that takes on a collaborative prescribing role. The alternative scenario assessed the benefits of introducing a pre-admission clinic pharmacy service where previously there had not been one. Probabilistic sensitivity analysis was conducted to explore uncertainty in the model. Results: In both the base-case scenario and the alternative scenario pharmacist prescribing resulted in an increase in the proportion of patients adequately treated and a decrease in the incidence of VTE resulting in cost savings and improvement in quality of life. The cost savings were $31 (95% CI: -$97, $160) per patient in the base scenario and $12 (95% CI: -$131, $155) per patient in the alternative scenario. In both scenarios the pharmacist-doctor prescribing resulted in an increase in QALYs of 0.02 (95% CI: -0.01, 0.005) per patient. The probability of being cost effective at a willingness to pay off $40,000 was 95% in the base scenario and 94% in the alternative scenario. Conclusion: Delegation of the prescribing of VTE prophylaxis for high risk surgical patients to a pharmacist prescriber in PAC, as part of a designated scope of practice, would result in fewer cases of VTE and associated lower costs to the healthcare system and increased QALYs gained by patients.