To determine the current prevalence of rheumatoid arthritis (RA) and rheumatoid factor positivity in the United Kingdom middle aged female population and to compare this with previous estimates to assess whether the disease is becoming less prevalent.
A cross sectional prevalence study was undertaken. All women aged 45-64 from the age and sex register of a large 11,000 general practitioner group practice in Chingford, East London were contacted and responders examined clinically and radiographically for the presence of RA by a single observer. Blood was also taken for rheumatoid factor testing (sheep cell agglutination test (SCAT), latex, and IgG). The prevalence in non-attenders was assessed from general practitioner and local hospital records. A diagnosis of definite or classical RA according to 1958 American Rheumatism Association criteria was used, and seropositivity was defined by a SCAT rheumatoid factor of 1/32 or more.
From the 1003 women examined (response rate of 78.8%), 12 women had definite RA (1.2%, 95% confidence interval 0.6 to 1.8). Of these, 7/12 had definite erosive changes on radiography and 3/12 had a positive SCAT (> 1/32). Three cases of RA were also found in the 284 non-responders (prevalence 1.1%) by case-finding techniques. The rate of SCAT positivity in the whole study group was 0.5%. The rates of RA and SCAT positivity currently found in this group were less than those obtained in previous surveys. In the only previous large scale United Kingdom survey, performed in the north of England between 1958 and 1960, 406 women aged 45-64 were examined and 10 cases of definite RA were found, a prevalence of 2.5%. In the patients with RA 68% had erosions and 63% positive SCAT. The population SCAT positive rate in this and other surveys sampled between 1954 and 1961 was in the range of 4-5%, since when there has been a progressive decline according to a number of other studies.
The prevalence of RA and rheumatoid factor in middle aged women is lower than previously believed and supports a variety of other data which indicate that RA is declining in incidence and severity.