Retrospective safety testing of the CT Clock method for identifying treatment-eligible patients with ischaemic stroke of unknown onset time: Study Protocol

More than 100,000 people in the UK have an ischaemic stroke every year. This means a blood clot blocks an artery supplying blood to their brain. Patients with ischaemic stroke often have sudden weakness affecting half of their body or face, and problems with speech, although other stroke symptoms are possible. Treatment with a clot-busting drug (thrombolysis) can reduce the amount of disability and death caused by ischaemic stroke by restoring the blood supply to the brain. Thrombolysis usually needs to be given within four and a half hours of stroke occurring. Unfortunately, nearly three quarters of patients with ischaemic stroke arrive in hospital later than this, or it is not clear when their stroke started. For these patients, it may still be possible to treat them with thrombolysis if the hospital can provide an additional advanced type of brain scan. However, many hospitals in the UK and worldwide cannot offer this advanced scan to patients with stroke, particularly hospitals that are not in major cities or developed nations. Patients arriving at these hospitals therefore do not currently have the same access to effective treatment for stroke. We have developed a simple method for identifying which patients can be given thrombolysis even if they arrive at hospital later than four and a half hours, or where there is uncertainty about when their stroke started. Our method does not require any additional or advanced imaging, only the standard computed tomography (CT or CAT) scan that all patients with stroke get when they arrive at hospital. Our method is called the CT Clock. We ask doctors to look for stroke changes indicating ischaemic stroke in the brain on CT. If they find these stroke changes, they measure them compared to normal brain. If the stroke changes on CT are minor (less than 20% darker than normal brain), or the scan appears normal despite quite severe stroke symptoms, we would consider these patients suitable for treatment with thrombolysis. This study proposes to test the safety of our CT Clock method in an analysis of existing NHS data from patients who have previously been treated with thrombolysis. We aim to show that when doctors who provide stroke care use our CT Clock method to identify suitable patients for treatment with thrombolysis, it is safe for these patients. If successful, this study will allow us to plan for and deliver future clinical testing where we would use the CT Clock to identify patients for treatment with thrombolysis in hospitals where advanced imaging for stroke is unavailable. Successful clinical testing is needed before our method can be used routinely in hospitals around the world. Data Study Protocol O_TBL View this table: org.highwire.dtl.DTLVardef@18a7b6corg.highwire.dtl.DTLVardef@ad2388org.highwire.dtl.DTLVardef@f7ea61org.highwire.dtl.DTLVardef@3cc038org.highwire.dtl.DTLVardef@6faf1e_HPS_FORMAT_FIGEXP M_TBL C_TBL