The Clinical and Cost-Effectiveness of Prehospital Triage and Bypass for Adults with Suspected Significant Traumatic Brain Injury

Background
Prehospital triage and bypass of patients with suspected significant traumatic brain injury (TBI) to distant neuroscience centres may improve outcomes by expediting access to specialist care. However, deterioration during prolonged primary transportation could risk secondary brain injury, while increasing the numbers of patients managed in specialist centres could increase health care costs. The aim of this thesis was to evaluate the clinical and cost-effectiveness of bypass to inform the organisation of NHS trauma services.

Methods
A cost-utility economic evaluation was undertaken using a probabilistic decision analysis model to collate and synthesise all relevant evidence. Four interventions applicable to NHS practice were compared: Prehospital triage and bypass; and three secondary transfer management strategies, defined according to referral patterns of TBI patients for neuroscience care (selective, routine and no transfer strategies). A series of studies were also conducted to guide model structuring, inform model parameterisation, and evaluate important components of the bypass strategy. The impact of parameter and structural uncertainty was investigated in a series of scenario, threshold and one-way sensitivity analyses. The expected net benefit of sampling (ENBS) from conducting a definitive trial of bypass was also examined.

Results
The base case probabilistic analysis suggested that routine secondary transfer may provide the optimal management strategy at a willingness to pay threshold of £20,000 (mean ICER £2,260). At a higher threshold of £30,000 prehospital triage and bypass was the most cost-effective option (mean ICER £27,158). At both thresholds there was considerable decision uncertainty, with a high probability of erroneously adopting a sub-optimal strategy (54% and 52% respectively). Sensitivity analyses demonstrated that this result was critically dependent on the parameterisation of costs and relative treatment effects. ENBS results suggested that, if feasible, a large scale trial examining the comparative effectiveness of bypass and selective secondary transfer is potentially cost-effective. In ancillary studies prehospital triage rules were found to have low sensitivity for significant TBI, no association was observed between emergency medical services interval and mortality, and a similar risk of deterioration was apparent in both bypassed and non-bypassed TBI patients.

Conclusions
Considerable uncertainty surrounds the optimal management pathway for patients with suspected significant TBI injured closest to a non-specialist hospital, and further research comparing bypass to secondary transfer strategies would have very high value to support decisions on reconfiguration of trauma services.