Predicting the Progression of Palindromic Rheumatism to Rheumatoid Arthritis: The Role of Ultrasonography and Anti-cyclic Citrullinated Peptide Antibodies

We investigated whether sonography and anti-cyclic citrullinated peptide (anti-CCP) antibodies in Chinese patients with palindromic rheumatism (PR) during active episodes are of predictive value for development of rheumatoid arthritis (RA). Clinically involved regions of 84 PR patients during active episodes were examined with ultrasonography using a 6–13 MHz linear transducer. Serum levels of anti-CCP antibodies were determined by enzyme-linked immunosorbent assay. All patients were followed up monthly for 3 years after investigation. Thirteen (15%) of the PR patients had progressed to RA after a mean of 1.4 years (range, 0.4–3.0 years). Of these 13 patients, 11 patients (85%) had sonographic features of synovitis and 8 patients (62%) had a positive anti-CCP antibody test. The absence of sonographic features of synovitis during active episodes provided a very high 3-year predictive value in excluding the possibility of progression to RA for PR patients with a negative anti-CCP antibody test. Both the sonographic findings of synovitis and a positive anti-CCP antibody test were significant predictors for progression of PR to RA within 3 years by backward stepwise logistic regression analysis. Sonographic examination together with an anti-CCP antibody test during active episodes is useful for predicting the progression of PR to RA.