Background/Purpose:

A number of patients with psoriatic arthritis (PsA) remain erosion-free despite years of disease. We aimed to determine the prevalence, characteristics and predictors of erosion-free patients (EFP) as compared to erosion-present patient (EPP) in PsA patients.

Methods:

This is a retrospective analysis conducted on all PsA patients with at least a 10 year period of follow-up in single centre PsA cohort.

Radiographs at 1–2 year intervals were scored (modified Steinbrocker): 0-normal, 1-soft tissue swelling/osteopenia, 2-erosions (E), 3- E plus joint space narrowing and 4- total joint destruction. EPP was defined as any joint with ≥ grade 2 (EFP could not have erosions at any visit).

T-tests, Chi-squared and Fisher’s exact test were used for comparison between groups. Baseline characteristics were used to predict the development of E with logistic regression models (reduced model using stepwise selection). The time to development of erosions was assessed with Kaplan-Meier estimator.

Results:

Among 290 patients, 12.4% were EFP and 87.6% EPP. EFP were diagnosed with psoriasis at a younger age compared to EPP patients, 22.5±14.7 and 27.6±12.1 years respectively (p=0.02). Of the 243 EPP patients, 97 (39.9%) have no E at first visit and develop it later. The remaining 146 (60%) already had E at first visit. There was no statistically significant difference in ethnicities, gender, age at diagnosis of PsA and duration of psoriasis and PsA among groups.

At baseline, EPP displayed a greater number of actively inflamed joints (10.1±9.1) compared to EFP (4.8±5.3) (p=0.0007). 40.6% of EPP had damaged joints compared to 8.3% in EFP (p=0.0002). EPP had a higher BMI compared to EFP (p=0.03). More EPP were on NSAIDs and sulfasalazine; p=0.04 and p=0.02 respectively. EFP were all employed vs. 69.8% EPP (p=0.05). 93% of EPP had active joints as compared to 72% EFP (p<0.0001). Similar differences in characteristics among EPP and EFP were also present at the last follow-up visit. In particular EPP have a higher percentage of unemployment as compared to EFP; 25% vs. 52% respectively (p=0.02).

Univariate analyses showed that actively inflamed joint count (OR=1.12, p=0.001), damage joint count (OR=2.35, p=0.02) and use of DMARDs/NSAIDs (OR=2.73, p=0.02) were associated with the development of E. In the multivariate analysis actively inflamed joint count (OR=1.09, p=0.01) and damage joint count (OR=2.43, p=0.02) were predictive of the development of E whereas a longer duration of psoriasis at baseline decreased the odds of developing E (OR=0.96, p=0.03). The mean time to development of E was 2.96±5.23 years (Figure 1).

Conclusion:

Among patients with PsA followed for at least 10 years 12% never develop E.

Presence of actively inflamed and damaged joints at baseline increases the odds of development of E. A longer duration of psoriasis at baseline has a protective effect of development of E.

Figure 1. Time to Development of Erosions