Annually 100,000 strokes occur, placing stroke as the largest cause of disability in the UK. 90% of strokes are preventable, leading to national focus on programmes including "The National Stroke Programme" to act on preventing, treating, and improving post-stroke care. Importantly, over 25% of ischaemic stroke sufferers have previously had a Transient Ischaemic Attack (TIA), which presents the biggest concern for TIA patients. There are no measures which reliably identify TIA patients most likely to suffer a stroke. Novel biomarkers for predicting stroke are key to addressing this problem. The PREDICT-EV study aims to screen 300 TIA patients and follow them over 12-months. The investigators will determine if a novel biomarker we've identified to increase thrombotic risk (endothelial derived extracellular vesicles) and the resulting increased prothrombin time is associated with patients at highest risk of stroke.

The inclusion criteria for phase 1 (initial patient recruitment) will be:

1. Patients with or without diagnosis of TIA made by a physician working in stroke medicine, sufficiently so to start post-TIA care or so that no further investigation is thought necessary to confirm or refute the diagnosis.
2. TIA confirmed patient has been prescribed antiplatelet drugs or anticoagulants.
3. Patients must be aged > 18 years.
4. Patients are taking an ordinary diet by mouth.

The inclusion criteria for phase 2 (patient representing with stroke) will be:

1. Radiological evidence, on CT and/or MR imaging of the brain of cerebral infarction, with or without secondary haemorrhage.
2. The underlying mechanism of cerebral infarction is embolic from a cardiac source (e.g. atrial fibrillation), atherothromboembolic (from aorta or other large vessels in the neck) or in-situ thrombosis. No further investigations are thought necessary to confirm or refute the diagnosis.
3. No further investigations are thought necessary to confirm or refute the diagnosis.
4. Patients must be aged >18 years.
5. Patients must not be pregnant or breast feeding.
6. Patients are taking an ordinary diet by mouth. Exclusion Criteria

The Exclusion criteria for phase 1 (initial patient recruitment) will be:

1. Inability to give consent.
2. Inability to feed by mouth.
3. Short life expectancy.
4. Pregnancy or breastfeeding.
5. Symptoms are readily explained by medical problems not involving focal cerebral ischaemia.

The Exclusion criteria for phase 2 (patient representing with stroke) will be:

1. Patients who have not previously given consent for follow up blood sampling.
2. Patients who are unable to feed by mouth.
3. Patients in whom life expectancy is short.
4. Patient is pregnant or breast feeding.

The sample will be selected from patients attending TIA clinic appointments, following primary care referral. Participants may also be identified from accident and emergency or following admission into hospital.