A recent study that evaluated the interaction of anticitrullinated protein antibody (ACPA) and rheumatoid factor (RF) in patients with rheumatoid arthritis (RA) found that combined ACPA and RF positivity was associated with an improved and more rapid response to antirheumatic medications.
ACPA and RF are predictive of the clinical course of RA; however, the incremental prognosis of both antibodies being positive in active established RA is unknown. A team of researchers led by Janet E. Pope of the Division of Rheumatology, University of Western Ontario, in Canada, conducted a study to evaluate the impact of both ACPA and RF in predicting sustained clinical response and to determine whether double-positive antibodies have a different effect on response to treatment compared with other combinations.1 The results were published in RMD Open.
The Ontario Best practices Research Initiative (OBRI) is a provincial registry that prospectively gathers long-term information on patients with RA followed in routine care. For this study, the analysis population was restricted to patients with available autoantibody information (ACPA and RF status), baseline Clinical Disease Activity Index (CDAI), and at least one follow-up assessment.
A total of 970 patients were included in the analysis, and patients were classified into one of four groups: (1) 262 patients (27%) were ACPAneg/RFneg; (2) 60 patients (6.2%) were ACPApos/RFneg; (3) 117 patients (12.1%) were ACPAneg/RFpos; and (4) 531 patients (54.7%) were ACPApos/RFpos. At baseline, significant differences were observed between groups in age, CDAI, tender joint count, and Health Assessment Questionnaire, with ACPApos/RFpos and ACPApos/RFneg patients being youngest and having the lowest disease activity and disability. Biologic use was reported in 20.2% of patients, but no differences were observed between groups.
CDAI was examined in two ways: (1) achievement of sustained remission, defined as at least two sequential visits separated by at least 3 and up to 12 months, with CDAI ≤ 2.8 and (2) change in CDAI from baseline as a continuous variable over time.
Next: the findings—and the implications for physicians
1. Pope JE, Movahedi M, Rampakakis E, et al. ACPA and RF as predictors of sustained clinical remission in patients with rheumatoid arthritis: data from the Ontario Best practices Research Initiative (OBRI). RMD Open. Published online Nov. 5, 2018. DOI: 10.1136/rmdopen-2018-000738.