THU0308 Calprotectin as a marker of disease activity in patients with new onset psoriatic and rheumatoid arthritis: correlation with ultrasonographic synovitis
Authors: G. Sakellariou, G. Lombardi, B. Vitolo, M. Gomarasca, M. Faraldi, R. Caporali, G. Banfi, C. Montecucco
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Serum Calprotectin has been tested as a marker of disease activity in psoriatic (PsA) and rheumatoid (RA) arthritis. In RA and in PsA on TNF inhibitors in remission calprotectin correlates with power-Doppler (PD) positive ultrasonographic (US) synovitis, while there is no data on untreated patients with new-onset PsA. <h3>Objectives</h3> To investigate the correlation and association between calprotectin and US synovitis in patients with new-onset PsA and in a control group of RA. <h3>Methods</h3> 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 synovitis scored 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 calprotectin concentration. Serum levels of calprotectin were 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 calprotectin concentrations and PD synovitis by regression analysis. Secondary analyses separating poliarticular and oligoarticular (SJC ≤4) PsA and using different definitions of synovitis (GS &gt;1, PD &gt;1) were performed. <h3>Results</h3> 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, calprotectin significantly 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 calprotectin and 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. Calprotectin showed 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, calprotectin levels did not associate with the presence of PD in PsA also when using a more stringent cut-off. Similar results were achieved in RA. <h3>Conclusions</h3> In untreated patients with early onset PsA, but not in RA, calprotectin correlates with US PD-positive synovitis, especially in poliarticular disease. Prospective studies are needed to confirm the use of calprotectin as a biomarker in early inflammatory arthritis. <h3>Disclosure of Interest</h3> None declared