One of the major barriers to the conduct of more and better randomised trials is the ever increasing cost of trials. Large trials of 10-15,000 participants typically cost in excess of £3-400m and there have been reports of single trials costing in excess of $1bn. These costs are unsustainable and distort the research agenda.
A major component of the cost of such trials is the setting up and running of large numbers of clinics. Clinics are required to screen and recruit participants and to monitor interventions by physical and laboratory means. Some commonly used interventions require no clinic monitoring so opening up the possibility of conducting a trial without the need for clinic visits. The ASCEND trial was conducted in 15,500 people with diabetes and compared using a 2×2 factorial design aspirin versus placebo and omega 3 fish oils versus placebo in reducing cardiovascular events. The trial was entirely mail based without the need for participants to attend clinics.
Potential participants with diabetes were identified from central registers and from GP practices. Letters of invitation included a screening questionnaire which was returned by post. Eligible participants were then entered into a pre-randomisation 2 month run-in phase where all participants received 8 weeks of placebo aspirin and placebo omega 3 fish oils. During the run-in phase participants were mailed a sample collection kit for blood and urine which was taken to their GP practice and returned by mail. A total of 4% of the potential participants invited went on to be randomised.
Follow-up takes place every 6 months with questionnaires being returned either by mail or online and by the time of the report of the main result the length of average follow-up was 7.4 years. The main results for aspirin and omega 3 fish oils can be found here and here.
The total cost of ASCEND is less than £10m, which makes it an order of magnitude less than similar sized clinic-based studies.