The prevalence of rheumatoid arthritis in Sweden.

The aim of this study was to ascertain the prevalence of rheumatoid arthritis (RA) in a Swedish general adult population. A questionnaire about chronic pain was mailed to a total of 3928 subjects who were chosen as a random sample of the population in two communities in the county of Halland. All persons answering affirmatively to questions intended to identify patients with RA were invited to a clinical examination. X-rays of hands and feet, and analyses of rheumatoid factor and C reactive protein were performed provided that the patients fulfilled two or more of the five clinical items of the 1987 ARA criteria. Furthermore, non-participants were searched for in a patient register and in medical records from the local rheumatology unit in an attempt to identify further cases. Using the modified 1987 ARA criteria for population studies the prevalence rate of RA was calculated to 0.51% (95%, CI = 0.31-0.79).