Rheumatoid arthritis in a medical information system: how valid is the diagnosis?

In order to validate the Stockholm County Medical Information System with regard to rheumatoid arthritis (RA) we have studied the medical records of 276 cases coded as RA in the medical information system. We searched information on the criteria for RA from (1961) and New York (1966). 18% of the medical records lacked information to the extent that an assessment of the number of criteria fulfilled was not possible. 9% fulfilled only one New York criterion and 7% fewer than three Rome criteria. 47% fulfilled four New York criteria and 35% at least seven Rome criteria. The most complete information on criteria was found in medical records from departments of rheumatology and these had also the highest degree of criteria fulfillment. A comparison is also presented between this sample of cases and a sample of RA persons selected from the general population with regard to fulfillment of criteria.