Comparative analysis of disease activity measures, use of biologic agents, body mass index, radiographic features, and bone density in psoriatic arthritis and rheumatoid arthritis patients followed in a large U.S. disease registry.

OBJECTIVE

To compare disease activity, radiographic features, and bone density in psoriatic arthritis (PsA) and rheumatoid arthritis (RA) matched cohorts.

METHODS

Disease activity and radiographic data in the Consortium of Rheumatology Researchers of North America database from 2001 to 2008 were compared for 2481 patients with PsA and 17,107 patients with RA subsequently matched for age, gender, and disease duration. Radiographic outcomes included presence of erosions, and joint deformity. In addition, bone mineral density (BMD) scores for lumbar spine (L-spine) and femoral neck were compared using the same matching criteria plus weight and smoking status.

RESULTS

Tender (4.5 vs 3.4, p < 0.001) and swollen (4.4 vs 2.9, p < 0.012) joint counts, and modified Health Assessment Questionnaire scores were significantly higher (0.4 vs 0.3, p < 0.001) in patients with RA compared with patients with PsA. Patient general health and pain scores were also higher in patients with RA vs patients with PsA. Joint erosions (47.4% vs 37.6%, p = 0.020) and deformity (25.2% vs 21.6%, p = 0.021) were more prevalent in RA than PsA. In multivariate analysis, a reduced prevalence of erosions in PsA vs RA was noted (OR 0.609, p < 0.001). After matching, T-scores for L-spine (-0.54 vs -0.36, p = 0.077) and femoral neck (-0.88 vs -0.93, p = 0.643) were similar in patients with RA and patients with PsA, although body weight was a major confounder.

CONCLUSION

The level of disease activity and radiographic damage was significantly higher for RA vs PsA subjects, although the magnitude of differences was relatively small. BMD levels were comparable between cohorts. Outcomes in patients with PsA and patients with RA may be more similar than previously reported.