Objective: To analyze longterm progression to rheumatoid arthritis (RA) and the predictive value of anticitrullinated peptide/protein antibodies (ACPA) in palindromic rheumatism (PR).
Methods: We selected all patients in our clinic with PR who had at least 1 ACPA measurement. We included only patients with pure PR, defined as no evidence of associated rheumatic disease at the first serum ACPA measurement. Clinical characteristics, serum ACPA levels, duration of PR until serum ACPA measurement, and total followup time were recorded. The outcome variable was the definitive diagnosis of RA. The prognostic value of ACPA status in pure PR for a definite diagnosis of RA was analyzed by different statistical methods.
Results: Seventy-one patients (54 women/17 men) with a PR diagnosis were included. Serum ACPA were positive in 52.1%. After a mean followup of 7.6 ± 4.7 years since the first ACPA measurement, 24 patients (33.8%) progressed to chronic disease: 22% RA, 5.6% systemic lupus erythematosus, and 5.6% other diseases. The positive likelihood ratio of ACPA status for RA was 1.45, and the area under the receiver-operating characteristic curve of ACPA titers was 0.60 (95% CI 0.45-0.75). Progression to RA was more frequently seen in ACPA-positive than in ACPA-negative patients (29.7% vs 14.7%), but the difference was not significant (hazard ratio 2.46, 95% CI 0.77-7.86). Mean ACPA levels of patients with pure PR did not differ significantly from those of patients who progressed to RA.
Conclusion: ACPA are frequently found in the sera of patients with PR, and a significant proportion of these patients do not progress to RA in the long term.