Randomisation is carried out by a telephone randomisation service (24-hour freephone number) or via a password-protected website via the internet. The collaborator is informed of the allocated treatment and the participant is ascribed a unique patient identifier number. The collaborator then either faxes or posts the randomisation form and the signed consent form to the ACST-2 trial office, which is based in the Nuffield Department of Surgical Science, University of Oxford, Oxford, UK. Procedural and post-procedure data are subsequently collected on a 1-month follow-up form completed by the collaborator and returned to the ACST-2 trial office. Data from these forms are entered on a trial database, which is held on secure servers on behalf of ACST-2 at the Clinical Trials Service Unit, University of Oxford, Oxford, UK [that have worked with us in designing and carrying out much of the work in the first Asymptomatic Carotid Surgery Trial (ACST-1) and ACST-2].
Annual follow-up of the patients in the trial is co-ordinated by the central ACST-2 office and annual questionnaires are sent either directly to the patient or to the collaborator, depending on local agreements.
Major events
These are classified as:
Information on these events is collected on the 1-month follow-up form or on the annual follow-up form. Further information, if required, is then requested from the collaborator. Once this information has been received by the ACST-2 office, a summary of the anonymised information is passed for adjudication. The Endpoint Review Committee reviews all such events and classifies the nature and severity of any of the strokes. Information on the types and number of major events is reviewed by the independent Data Monitoring Committee.
