The characteristics of a national register of people with multiple sclerosis (MS): a comparison between the ARMS (Action for Research into Multiple Sclerosis) register and 10 British MS populations.

Problems with case ascertainment in epidemiological research on multiple sclerosis (MS) make it necessary to use indirect sources. However, there is a lack of information about the characteristics of cases drawn from different sources and thus little basis on which sampling frames for large scale surveys may be constructed. The characteristics of a population drawn from the membership of Action for Research into Multiple Sclerosis (ARMS) were compared with those of 10 other British MS populations reported between 1980 and 1987. Demographic variables examined were geographical location, nationality, ethnicity, sex ratio and age. Diagnostic status, age at diagnosis and duration since diagnosis were considered together with data on the comparative populations based on date of onset. On all the variables investigated the ARMS population fell close to or within the range shown by the comparative populations. The relative youth of the ARMS population and its bias towards a high proportion of females were differences in keeping with existing knowledge about the membership of mutual support organisations. A population drawn from such an organisation may usefully complement other MS research populations provided that the likely biases in each are understood.