Methods: Prospective observational study. Population: Patients diagnosed with RA, in clinical remission, receiving adalimumab (ADL) or etanercept (ETN) with EIA. Clinical activity was assessed by DAS28-ESR, DAS28-CRP, CDAI (Clinical Disease Activity Index) and SDAI (Simple Disease Activity Index) scores at each visit. Twelve-joint ultrasound assessment (elbows, wrists, 2nd and 3rd metacarpo-phalangeal, knees and ankles)  was performed evaluating synovitis through B-mode (BM) and Color Doppler signal (CD). A BM and CD score was calculated summing the highest score from each joint to a maximum of 36 points. The sonographer was blinded to the clinical and laboratory data. Serum drug levels were measured using Promonitor® ELISA kits (Progenika Biopharma - Grifols, Spain). 

Results: A total of 34 patients were included since February 2011 to January 2016. One patient was excluded due to blindness violation and 2 patients never reduced anti-TNFα due to low drug levels. 27 patients were women (79,4%) and the mean age was 61 years. Most patients were RF positive (85,3%) and ACPA positive (74,2%). 18 patients were with ADL treatment and 16 with ETN. 28 patients (82,35%) were with DMARD concomitant treatment (14 MTX, 11 LEF, 2 HCQ, 1 SSZ) and 7 patients were with low-dose CS. Mean time from diagnosis was 15,19 years (range 2,15 – 52,31) and Mean time with current biologic drug was 4,11 years (range 1,39 – 11,07). Nine patients (26,5%) returned to standard interval due to worsening of clinical activity and one discontinued treatment due to septic arthritis. 

Clinical activity scores, ultrasound scores and drug levels are summarized in table 1. 

Table 1. Clinical activity scores, ultrasound scores and drug levels. 

BM: B-mode; CD: Color Doppler; ADL: adalimumab; ETN: etanercept; *p<0,05; **p<0,005. All results mean (SD) otherwise specified. 

Conclusion : 1. Clinical remission was sustained in most patients receiving ADL or ETN in extended interval of administration. 2. Some patients (26,5%) returned to standard interval of administration due to clinical worsening. 3. Some patients show subclinical ultrasound synovitis in B-mode or Color Doppler from baseline, although we found no significant worsening over time. 4. Drug levels decrease over time as we extend interval of administration. 5.  It would be advisable to perform periodic ultrasound and monitoring of anti-TNFα levels to maintain clinical remission in patient with extended interval of administration. 

Acknowledgements: This study was supported by a research grant from Fundación Española de Reumatología and Asociación para la Investigación en Reumatología Marina Baixa (AIRE-MB).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-activity-ultrasound-assessment-and-drug-monitoring-in-rheumatoid-arthritis-patients-receiving-anti-tnf-%ce%b1-therapy-with-extended-interval-of-administration/