Validating the portal population of the United Kingdom Multiple Sclerosis Register.

•Validation of a self declared MS Population with a clinically diagnosed one.•We analysed the UK MS Register for a number of key characteristics. The internet (n = 11,021) and clinical (n = 3,003) populations were studied for key shared epidemiology. We found them to be closely matched for mean age at diagnosis (clinical = 37.39, portal = 39.28) and gender ratio (female %, portal = 73.1, clinical = 75.2)•There is a representative population of people with MS in the online element of the UK MS Register – The MS Register can be utilised as a valid cohort for Clinical and PRO research•Kernel Density of the populations for age can be seen in the graphs: