Objectives To study the relationship between serum trough levels of TNF antagonists -etanercept (ETN), adalimumab (ADA), infliximab (IFX)- and subclinical active-synovitis (SAS) by ultrasound (US) in patients diagnosed with RA and PsA in clinical remission (CR) or low disease activity (LDA).

Methods Prospective, multicenter study of patients diagnosed with RA or PsA attended by three hospital outpatient clinics in Catalonia, Spain treated with ADA, ETN or IFX for ≥3 months in CR or with LDA measured by DAS28-ESR in ≥2 consecutive visits. We determined serum trough levels (commercial ELISA Kit Promonitor®, Progenika SA) at 0, 4, 8 and 12 months of follow-up. Optimal cut-off trough levels for ADA were (>1.274 μg/ml), ETN (>1.242 μg/ml) and IFX (>1.5 μg/ml). Sonography of fingers and wrist joint of each hand was performed. Synovial hypertrophy (SH) and power Doppler signal (PD) for synovitis was evaluated at 0 and 12 months. SH plus PD signal was considered as SAS and a total synovitis score was calculated. We present the results at study entry (visit 0).

Results Of 165 patients included, 100 (46 RA, 54 PsA) underwent US examination: 62% female, mean age 57±13 years, mean DAS28-ESR 2±0.5, 77% CR and 23% with LDA, 51% on monotherapy (26% RA, 72.2% PSA), 46% receiving low dosage of biologic (32.6% RA, 57.4% PsA), and taking ADA (35), ETN (50) and IFX (15). SAS was found in 45 patients (31 RA and 14 PsA), representing 42,8% of patients treated with ADA, 46% ETN, and 46,6% IFX. Total subclinical synovitis score was 8±6.3. No significant differences were observed in mean SDAI, ESR, CRP, DAS28-ESR, drug serum trough levels or percentage of suboptimal trough anti-TNF serum levels between patients with or without US SAS. After using a logistic regression model, only diagnosis of RA, but not drug serum levels was significantly associated with the presence SAS. No significant correlation between total synovitis score and drug levels were found.

Conclusions Subclinical synovitis by US is frequent in patients with RA or PsA receiving TNF who achieve good disease control. Drug serum levels of TNF antagonists do not correlate with subclinical synovitis in these patients.

References

1. Chen D-Y, et al. Ann Rheum Dis 2014;0:1-9

Disclosure of Interest J. Inciarte-Mundo Grant/research support: Grant from Hospital Clinic of Barcelona (Premi Emili Letang 2013), J. Ramirez Garcia: None declared, P. Estrada Alarcόn: None declared, M. Garcia Manrique: None declared, A. Gonzalez Navarro: None declared, C. Saura: None declared, J. Narvaez Grant/research support: Unrestricted grant from Pfizer, J. Rodríguez-Moreno Grant/research support: Unrestricted grant from Pfizer, A. Gόmez-Centeno Grant/research support: Unrestricted grant from Pfizer, J. Yagüe Grant/research support: Unrestricted grant from Pfizer, J. Cañete Grant/research support: Unrestricted grant from Pfizer, R. Sanmarti Grant/research support: Unrestricted grant from Pfizer

DOI 10.1136/annrheumdis-2014-eular.3604