Clinical arthritis associated with positive radiological and serological findings in Finnish adults.

The Mini-Finland Health Survey was designed to analyse the epidemiology of major public health problems. The study covered a representative sample of the Finnish population aged 30 years or over, and initially comprised 8,000 people. Serum rheumatoid factor was determined in 7,124 cases (89%). There were 138 cases of clinical arthritis in the series, corresponding to a prevalence of 1.9% (1.0% in males and 2.7% in females). Fifty-nine of the cases (0.8% of the population) were seropositive, and 50 cases (0.7%) had in their hand radiographs changes characteristic of rheumatoid arthritis. Twelve of the X-ray positive cases were seronegative. One-half of these proved to be seroconversion cases or rheumatoid variants typically seronegative, such as early-onset juvenile rheumatoid arthritis.