THU0308 Calprotectin as a marker of disease activity in patients with new onset psoriatic and rheumatoid arthritis: correlation with ultrasonographic synovitis

Background Serum Calprotectinhas been tested as a marker of disease activity in psoriatic (PsA) and rheumatoid (RA) arthritis. In RA and in PsA on TNF inhibitorsin remission calprotectincorrelates with power-Doppler (PD) positive ultrasonographic (US) synovitis, while there is no data on untreated patients with new-onset PsA. Objectives To investigate the correlation and association between calprotectinand US synovitisin patients with new-onset PsA and in a control group of RA. Methods Consecutive patients with PsA and a group of age and gender-matched patients with RA, referred to an early arthritis clinic (2005–2014) were included. Demographic and clinical features, including a 44 joint count for tenderness and swelling (TJC, SJC) and C-reactive protein (CRP) were recorded. US of wrists (radiocarpal, intracarpal and ulnocarpal) and MCP joints with grey scale (GS) and PD synovitisscored 0–3 at each site, with a total score from the sum of each site, was available at the same time, as well as serum samples to measure calprotectinconcentration. Serum levels of calprotectinwere compared by Mann Whitney test in PsA and RA. The correlation between calprotectin, TJC, SJC, CRP and US PD and GS was evaluated by Spearman’s correlation coefficient, while the association of calprotectinconcentrations and PD synovitisby regression analysis. Secondary analyses separating poliarticular and oligoarticular (SJC ≤4) PsA and using different definitions of synovitis(GS >1, PD >1) were performed. Results 156 patients (78 PsA and 78 RA) were included (RA: male 28.2%, mean (sd) age 51.9 (13.3); PsA male 32%; mean age 51.7 (13.5)). Patients with RA had significantly higher CRP (median, IQR) (0.6, 0.3–2.1 vs 0.36, 0.3–1, p 0.04), SJC (7, 5–12 vs 6, 3–9, p 0.008), GS (6, 4–11 vs 5, 2–7, p 0.01) and PD (2, 0–9 vs 1, 0–3, p 0.003) scores. Calprotectin(ng/ml, median, IQR) did not significantly differ in PsA (3123, 2063–4669) and RA (2556, 1615–4441), also when separating poliarticular and oligoarticular PsA. In patients with PsA, calprotectinsignificantly correlated with GS score (rho 0.340, p 0.007), PD score (rho 0.290,p 0.02) and with the presence of PD ( categorical variable) (rho 0.263, p 0.04), while in RA there were no statistically significant correlations. When separating poliarticular and oligoarticular PsA, a significant correlation between calprotectinand GS score (rho 0.369, p 0.01) and PD score (rho 0.363, p 0.02) was confirmed in poliarticular but not oligoarticular disease. In both RA and PsA SJC and TJC did not significantly correlate with calprotectin. Calprotectinshowed a statistically significant correlation with CRP in both PsA (rho 0.273, p 0.01) and RA (rho 0.27, p 0.01), showing concurrent validity. In regression analysis, calprotectinlevels did not associate with the presence of PD in PsA also when using a more stringent cut-off. Similar results were achieved in RA. Conclusions In untreated patients with early onset PsA, but not in RA, calprotectincorrelates with US PD-positive synovitis, especially in poliarticular disease. Prospective studies are needed to confirm the use of calprotectinas a biomarker in early inflammatory arthritis. Disclosure of Interest None declared