Background Anti-citrullinated peptide antibodies (ACPA) have been considered a relatively specific marker for rheumatoid arthritis (RA), and may play a role in its pathophysiology. ACPA has been found at a greater prevalence among PsA patients (approximately 8% or more)1 than in the general population. Also, ACPA have been isolated from the synovial fluid of PsA patients2. Several reports have suggested that PsA patients with positive ACPA may have greater swollen/tender joint counts with more deformities than ACPA negative PsA patients3,4,5;other studies have suggested no difference1,6.
Objectives To determine what clinical features differ between ACPA (+) and ACPA (-) PsA patients.
Methods A cross sectional study of patients with physician diagnosed PsA in the CORRONA database, a large national registry of patients with RA and PsA. ACPA (+) and ACPA (-) PsA patients were evaluated for differences in disease activity, disease severity and immunomodulatory medication use. Evaluations included: tender joint count, swollen joint count, HAQ, patient global assessment, physician global assessment, DAS 28, CDAI, presence of enthesitis, presence of dactylitis, skin psoriasis activity, presence of Sjogrens symptoms, and radiographic changes (defined by presence or absence of erosions, joint space narrowing and joint deformity). ACPA (+) and ACPA (-) groups were also assessed for the presence of rheumatoid factor (RF) and repeat analysis was done to determine if RF presence contributed to any differences. Statistical methods included Pearson’s-chi-square test, Fisher’s exact test and one way ANOVA.
Results Through 2012, a total of 5363 PsA patients were identified in the CORRONA database. 17.7% of the PsA patients had test results for ACPA: 842 were ACPA (-) and 116 ACPA (+). There was no significant differences in any measures of disease activity or disease severity (including radiographic changes) or the use of immunomodulatory medications between ACPA (+) and ACPA (-) patients. Further stratification into subgroups based upon the presence of RF did not reveal any clinically important differences.
Conclusions In a large cohort of PsA patients in clinical practice, there were no differences in disease activity, disease severity (including radiographic changes) or the use of immunomodulatory medications between ACPA (+) and ACPA (-) PsA patients. The data suggest that different than for RA, the presence of ACPA(+) may represent only an epiphenomenon in PsA.
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Disclosure of Interest D. Huynh: None Declared, C. Etzel Employee of: Corrona, V. Cox Employee of: Corrona, J. Kremer Shareholder of: Corrona, Employee of: Corrona, J. Greenberg Shareholder of: Corrona, Consultant for: Astra Zeneca, Novartis, Pfizer and Corrona, A. Kavanaugh: None Declared