Background The relationship between anticitrullinated protein antibodies (ACPA) and the clinical outcome of rheumatoid arthritis (RA) under treatment has been evaluated in clinical trials with conflicting results. Thus, an analysis of the BeSt study indicated that response to treatment was similar in ACPA-positive and ACPA-negative patients (van den Broek et al, Ann Reum Dis 2012; 71: 245–248). However, ACPA-positive patients showed more frequently radiological damage progression. On the contrary, in the IMPROVED study, ACPA-negative patients achieved less remissions on treatment than ACPA-positive patients (Wevers-de Boer et al, Ann Reum Dis 2012). Because of these, we evaluated the clinical response of patients with RA receiving treatment according to ACPA titers.
Patients and Methods This was a retrospective longitudinal observational study. We included all patients seen at our Unit who fulfilled the following criteria: 1) Diagnosis of RA by a rheumatologist meeting the 1987 criteria for RA; 2) Available determinations of ACPA; 3) Treatment for AR (whether or not biological therapy) with a minimum follow up of 6 months. The outcome variable was clinical regression defined as reaching DAS28 ≤ 2.6. Predictors of the outcome variable were evaluated using logistic regression models adjusted by gender and age.
Results 71 patients were included, 79% of them women. Clinical regression was observed in 42 (59%) patients during the first 12 months of follow-up. Baseline median (IQR) ACPA levels were 363 (27.7–500) for individuals without clinical regression and 91.7 (7–458) for those with regression (p = 0.045). 19 (66%) patients without regression versus 15 (36%) with regression showed ACPA levels ≥200 (p = 0.013). 6 (20%) patients without clinical response versus 18 (42%) individuals with response showed negative ACPA titers (p = 0.050). Factors independently associated with clinical regression were: Recent onset RA [adjusted odds ratio (AOR) 5; 95% confidence interval (95%CI) 1.01–25; p = 0.049], baseline ACPA levels ≥200 [AOR 0.13; 95%CI 0.03–0.5; p = 0.004], baseline CRP levels [per unit increase; AOR 0.94; 95%CI 0.91–0.99; p = 0.024], baseline DAS28 [per unit increase; AOR 0.47; 95%CI 0.25–0.89; p = 0.021].
Conclusions ACPA levels can predict clinical regression of patients with RA receiving treatment in real life conditions. Individuals with high ACPA levels may benefit from a more aggressive treatment approach. ACPA titers may be useful to monitor the clinical activity of RA.