Evolution of the rheumatoid factor over time.

With purpose to verify the epidemiological value of the Rheumatoid Factor's variations over time, we studied: 421 RA at first hospitalization (from 1976 to 1985; Group A); 348 consecutive RA with follow-up at 0, 6, 12, 24, and 48 months (Group B); 750 subjects, chosen at random from a healthy population, before and after 48 months (Group C). Five agglutination tests were used: three latex tests with human (2) and rabbit (1) IgGs; one red cells test on slide, and one in tube. The results were: uneven variations in positive results in all tests (Group A); the maximum confirmation of the basic profile are provide in short-term follow-up; in subsequent follow-ups, with the exclusion of the case of all the negative tests, the remaining profiles have a decreasing confirmation rate (Group B); the positive frequency is different in all the tests; this trend is sustained at follow-up (4 years later) in spite of the overall increase of positive results (Group C). Serum-positive RA, according to all or many tests, tend to reduce the number of positive results; healthy subjects (with few positive tests) tend to increase the number of positive results over time. RA with all the negative tests have a reasonably constant profile.