Transition from genetic risk to the development of systemic autoimmunity associated with rheumatoid arthritis (RA) is considered a key step for the development of RA and often referred to as the immune onset of the disease. The aim of this study is to identify predictors for the presence of anticitrullinated protein antibodies (ACPA) as a marker of systemic autoimmunity associated with RA in a high-risk population, an ongoing cohort of first-degree relatives of patients with RA. We assessed the presence of ACPA in individuals without clinical evidence of RA. We examined characteristics associated with ACPA positivity using general estimation equations to account for multiple observations per individual. A total of 1159 serum samples from 1025 subjects were analyzed, 69 samples (6%) were ACPA-positive, and 227 (20%) positive for rheumatoid factor. Participants had a median age of 45 years (interquartile range (IQR): 33-55) at baseline and 76% were women. Overall, ACPA positivity increased with age (p < 0.001). Among women, ACPA positivity was particularly associated with the age group 45 to 55 years (p = 0.003), but not among men (p = 0.7). In multivariable adjusted analyses, age older than 45, female sex and tobacco smoking were independently associated with ACPA positivity. In our cohort, the presence of ACPA was associated with older age and peaked in women around age 45 to 55 years, the perimenopausal period, suggesting that the development of ACPA may be favored by the decline in ovarian function.
Keywords: Autoantibodies; Epidemiology; Observational studies; Rheumatoid arthritis.