Feasibility Study of the CT Clock Tool for Estimating Onset Time of Ischaemic Stroke: Study Protocol

Ischaemic stroke is a devastating disease with high rates of death and disability affecting ∼100,000 people annually in the UK. Effective treatments are only offered when the time of stroke onset is known and within specific limits. For the 20% where onset time is unknown or delayed, advanced imaging methods can identify people for safe and effective treatment. However, this advanced imaging is not widely available. We have developed a method for identifying patients who can still be treated even without advanced imaging. The CT Clock Tool uses only the non-enhanced CT brain scan, that most patients with stroke receive upon arrival at hospital, to determine whether patients are eligible for treatment.

This project aims to provide the first prospective clinical testing of the CT Clock Tool in a single-centre feasibility analysis. We will recruit patients in the emergency department with ischaemic stroke and obtain consent to use their acute CT brain imaging and other data relating to their care. We will ask treating clinicians to apply our CT Clock Tool method in real time, but we will not alter routine care pathways or otherwise involve patients. We have powered the study to validate previous estimates of the diagnostic accuracy and precision of our method for identifying treatment eligible patients. Results from this project will enable a future definitive randomised-controlled trial, which if successful would allow the routine use of our method anywhere CT brain imaging is available for patients with stroke.