Background/Purpose: Psoriatic arthritis (PsA) belongs to the group of the spondylarthropathies. It is associated with psoriasis and typically seronegative for autoantibodies. PsA disease activity can be measured using the Disease Activity in Psoriatic Arthritis (DAPSA) score which is based on both clinical (e.g., swollen joint count, SJC) and systemic (e.g., C-reactive protein, CRP) markers of inflammation. However, the impact of clinical and systemic inflammation on structural progression is unclear. In this analysis, our aim was to determine the contribution of clinical and systemic inflammation to structural progression of patients with PsA.

Methods: In a secondary data analysis, we analyzed patient data from the IMPACT 2 trial of infliximab (INF) vs. placebo (PLC) in patients with established PsA (disease duration in years: INF: 7.5±7.8, PLC: 8.4±7.2). Concomitant methotrexate treatment was allowed but not mandatory in both treatment arms. We obtained modified Sharp-van-der-Heijde scores from X-rays performed at baseline and after one year to compute radiographic progression. We further extracted levels of SJC and CRP and calculated time-averaged SJC (taSJC) and CRP (taCRP) values to reflect the clinical and systemic inflammation, respectively. In a multivariable binary logistic regression model, we assessed the impact of taSJC, taCRP, and their interaction, on structural progression. Next, we divided patients into different subgroups depending on their taSJC and taCRP levels into active (+) or inactive (-). We tested whether radiographic progression was different in taSJC+ vs. taSJC- and taCRP+ vs. taCRP- using the Mann-Whitney-U-test.

Results: We analyzed available data of 151 patients (76 PLC, 75 INF). Patients in the INF arm showed no radiographic progression (-1.16±3.96), while patients in the PLC arm showed little progression (0.74±2.98). We therefore focused on the 76 PLC patients. Despite the small overall progression, taSJC, taCRP, and their interaction were associated with radiographic progression (OR for taSJC: 1.24, CI 95 %: 1.04-1.47, p=0.016; OR for taCRP: 6.08, CI 95%: 1.12-33.03, p=0.036; interaction term: p=0.097). Radiographic progression was higher in taSJC+ patients compared to taSJC- patients (1.05±3.21 and 0.56±2.30, respectively; p=0.016), as well as numerically higher without statistical significance in taCRP+ vs. taCRP- patients (1.14±3.23 and 0.05±2.37, respectively; p=0.532). Also, despite the limited power of subgroup analyses, there was evidence that SJC activity plays a role in CRP- patients (p=0.076), whereas CRP activity seems to be of less importance SJC- patients (p=0.643).

Conclusion: In patients with PsA, both clinical and systemic inflammation have impact on structural progression; in patients without systemic inflammation, clinical joint activity may still be considered as a risk factor for progression.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/predictors-of-structural-progression-in-psoriatic-arthritis-clinical-versus-systemic-inflammation/