Validation of the Medical Research Council prion disease rating scale in France

The development of assessment tools other than survival time is necessary to conduct therapeutic trials in prion diseases (also known as subacute transmissible encephalopathies). The Medical Research Council Prion Disease Rating Scale published by Thompson et al. (The Medical Research Council prion disease rating scale: A new outcome measure for prion disease therapeutic trials developed and validated using systematic observational studies. Brain. 2013; 136: 1116–27.) is the first attempt at a specific evaluation of prion diseases to avoid the floor effect seen in other scales. Validation of this scale in other countries is essential because, given the rarity of these diseases, therapeutic trials are likely to be multi-centre and international. After translation into French, we assessed by phone 173 cases classified as sporadic Creutzfeldt–Jakob disease out of 852 patients notified to the French national surveillance network between November 2014 and May 2021. Data showed that the natural history of the disease is similar in the UK and France. Patients who have a heterozygous genotype at codon 129 of the prion protein gene have a slower decline than homozygous patients. In rapidly progressing patients, death occurs shortly after reaching a low score or after a ‘pre-terminal plateau’ at a very low score. The similarities of disease progression profile observed in France and the UK with somewhat different surveillance systems and by distinct procedures highlight the robustness of the Medical Research Council Prion Disease Rating Scale that can be thus used to define primary endpoints of future trials at the international level.