UK ACST-2 participants – information on fair processing of data

Stroke is the third leading cause of death and disability worldwide. Around one quarter of strokes are caused by fatty deposits (atheroma) building up in the carotid arteries, which are the main blood vessels in the neck that supply blood to the brain. This condition (which is called carotid stenosis) does not usually cause any symptoms unless or until bits of the atheroma fall off, lodge in the brain and cause a stroke or mini-stroke.

To prevent this happening, very large numbers of patients undergo carotid intervention each year. The standard operation is called carotid endarterectomy (CEA), which involves surgical exposure of the carotid artery, opening it and removing the fatty deposits. An alternative technique is carotid artery stenting (CAS), which is an X-ray guided technique in which a stent is inserted into the carotid artery via a blood vessel in the groin. Both procedures are performed widely, and whilst there are infrequent complications associated with both procedures, both reduce the long-term risk of stroke. However, whilst carotid surgery and stenting are both ‘good’, it is not clear which provides the most durable protection against stroke.

The aim of ACST-2 (ISRCTN 21144362) is to compare the long-term benefits of carotid surgery with carotid stenting. Each summer, questionnaires are mailed to ACST-2 participants asking them to report any strokes or repeat carotid procedures since their trial procedure. English trial participants are ‘flagged’ with NHS Digital to both obtain details on cause-specific mortality allowing us to identify those who have suffered a fatal stroke, and also to avoid sending questionnaires to participants who have died.

Once a year we will provide NHS Digital with first and last name, date of birth and NHS number of English ACST-2 study participants who have not withdrawn from ACST-2. The ONS mortality data is provided by NHS Digital on behalf of ONS and is sourced from Civil Registration Data. This patient identifiable data will be imported into an existing, empty ACST-2 database held securely by The University of Oxford (Data Controller), and used solely for academic research purposes by the study team in Oxford. Before analysing this complete dataset patient identifiers will be removed. Importantly, whilst the information received is specific to each trial participant, no individual person will be identifiable in any publication arising from this work. Furthermore, the ACST-2 database will not be shared with organisations outside of the University of Oxford and only accredited researchers in ACST-2 group based at the University of Oxford will have access to the data. Anonymous results of the study may be made available to ACST collaborators and relevant bone fide researchers according to the Nuffield Department of Population Health (NDPH), University of Oxford data sharing policy:

What to do next?

UK ACST-2 participants originally consented to their centrally held medical records being accessed and do not need to take any further action if they agree to the data linkage proposed.

However, if participants decide they do not want their study data to be linked in this way they can withdraw from ACST-2 by contacting the ACST trials office:


or Tel: +44 (0)1865 61 79 79 between 9am-4pm on weekdays