Clinical rheumatoid arthritis (RA) is preceded by an immunological process. Our objective was to investigate C-reactive protein (CRP) for its prediction of RA.
A case-control study was nested within a Finnish cohort of 19,072 adults who had no arthritis and no history of the disease at the baseline examination conducted between 1973 and 1977. By late 1989, 124 had developed RA. Three controls for each incident case were individually matched for sex, age, and municipality. The CRP concentration was measured by a sensitive ELISA.
No difference was noted in serum CRP levels between cases and controls. The odds ratios (95% confidence intervals) of RA in the quintiles of CRP were 1.0, 0.89 (0.45-1.76), 1.11 (0.59-2.08), 0.99 (0.51-1.91), and 0.95 (0.49-1.87). Similarly, there was no difference when the data were analyzed in strata of sex, age, rheumatoid factor (RF) status at baseline, and length of time from taking the specimens to the onset of clinical disease.
Pre-rheumatoid immunological process as reflected in RF production is not associated with any marked inflammation or tissue injury heightening CRP.