Prevalence of rheumatoid arthritis in urban and rural populations in South Wales.

The wide range of estimates of the prevalence of rheumatoid arthritis which is evident from a study of surveys undertaken in Great Britain and other countries (Cobb and Lawrence, 1957; Cobb, Warren, Merchant, and Thompson, 1957) is open to two interpretations: either large regional differences do exist or the diagnostic criteria adopted in these surveys are insufficiently standardized for valid comparison of the findings. Though the former explanation may be the correct one, the latter is certainly true also, and differences reported at present can be attributed as much to diagnostic criteria and population selection as to true epidemiological variations in prevalence. In a first attempt to remedy this deficiency, the Manchester University Rheumatism Centre and the Medical Research Council's Pneumoconiosis Research Unit have pooled their resources and carried out a number of population studies (Miall, Caplan, Cochrane, Kilpatrick, and Oldham, 1953; Kellgren and Lawrence, 1956). In this paper we summarize the results of two of these co-operative investigations. More detailed accounts of some of this work have already been published (Ball, 1955; Miall, 1955); reports of other joint studies will follow. The purpose of this paper is to describe the material from these two studies as a whole, and to discuss the validity of the diagnostic criteria used and methods of population sampling for this type of work.