Background The UK Multiple Sclerosis Risk–sharing Scheme (RSS) was established in 2002 following NICE's decision that the cost–effectiveness of interferon (IFN)–β and glatiramer acetate (GA) could not be assessed with existing short–term data. The scheme was set up as a joint undertaking between the Department of Health and the manufacturers of the drugs with input from other stakeholders. The purpose was to ensure cost–effective provision of IFNβ/GA to eligible people through a number of mechanisms, including an initial recalculation of drug pricing and the establishment of specialist nursing and medical structures. One aspect of the scheme was the enrolment of a cohort of at least 5000 people commencing IFNβ/GA with follow–up for 10 years, using these data to adjust drug costs.

Methods Patients were enrolled prospectively from 72 UK sites. Baseline demographic data, history, eligibility and EDSS were recorded. Patients were invited to annual review as part of routine care with information recorded on relapses, type of MS, treatment history and EDSS. Efforts were made to maximise retention, including creating the facility for telephone follow–up and EDSS scoring. From 2006, data has been collated by PAREXEL. Following recognition of limitations in the original design, the protocol and statistical analysis plan have undergone revision with input from a newly established, independent Scientific Advisory Group.

Results From May 2002 –April 2005, 5610 people with MS consented to participate in the RSS, representing approximately 80% of people starting IFNβ/GA within this period. In December 2012, 4673 remained within the scheme (83.3% retention). Of those no longer within the scheme, 349 (6.2%) have been lost to follow up and 585 (10.4%) have withdrawn consent. Year 10 data has already been submitted on the earliest enrolled and over half the 10 year data should be collected by the end of 2013. By January 2013, we have, in total, 31,874 submitted annual reviews with a further 6092 accounted for as missed visits. All data has been validated and reviewed by data management and any discrepancies reconciled with the sites.

Discussion In spite of the short start–up time and ambitious scope of the RSS, this represents a collective effort by UK physicians to recruit and retain the biggest MS treatment cohort worldwide. While it might have been expected that delays in presenting data would adversely affect retention and motivation, drop–out rates are lower than would be predicted from analogous non–interventional studies. Joint analysis of the 4 and 6 year data is due later in 2013 and data collection will be complete by 2015. In order to fulfil our obligations to the scheme, it is important UK neurologists maintain this level of achievement.