Background Both serum drug level testing (1) and ultrasound joint evaluation (2) might be usefull to increase the accuracy of correct evaluation of the response to treatment in patients with rheumatoid arthritis treated with biologics.

Objectives To evaluate the possibile correlations between serum drug level of anti TNF drugs and ultrasound evaluation in rheumatoid arthritis patients treated with etanercept (ETA), adalimumab (ADL) and infliximab (IFX).

Methods 52 consecutive rheumatoid arthritis patients on stable anti TNF treatment for more than 6 months were evaluated. Clinical and US evaluation was performed by two independent assessors, the same day as all laboratory tests. US of boths hands (dorsal wrist, 2nd to 5th volar metacarpophalangeal and 2nd to 4th volar proximal interphalangeal) was performed with an ESAOTE MY LAB70 machine using a linear probe of 15 MHz. Synovial hypertrophy and power Doppler (PD) signal were scored (grades 0–3). Synovial hypertrophy >2 plus power Doppler signal was classified as active synovitis. Serum drug level was measured just before the next iv infusion or sq injection by ELISA Kit Promonitor®, Progenika SA for ETA, ADL, IFX. All patients were divided in two groups according to the detectable or undetectable serum drug level. Statistical analysis was performed using IBM SPSS v20.0.

Results All of the patients included had the biologic associated to DMARD, 80.8% were females, mean age 60.44 (11.39), mean disease duration 13.08 (7.05). 53.8% (28) patients were treated with ETN, 34.6% (18) with ADL and 11.5% (9) with IFX. All ETN patients, 61.11% ADL and 57.14% IFX patients had dosable drug level. No statistical significant difference between dosable and undosable drug level was found regarding age, disease duration, rheumatoid factor or ACPA positivity. The presence of dosable drug level negativelly correlated with markers of inflammation, ESR (p=0.030, r-0.357) C reactive protein (p=0.016, r-0.394), physician global assessement (PGA p=0.034, r-0.349). Regarding US parameters (see table) the only significant correlation was found between the number of PD joints and undetectable drug level. There were no statistically significant differences between anti TNF antagonists used.

Conclusions Drug serum levels of TNF antagonists correlates with markers of inflammation, number of power Doppler joints but not with total power Doppler score or total Grey scale score.

References

1. Krieckaert, C et al. Personalised treatment using serum drug levels of adalimumab in patients wih rheumatoid arthritis:an evaluation of costs and effects. Ann Rheum Dis Nov 21,2013;

2. Ramirez J et al, Patients with rheumatoid arthritis in clinical remission and ultrasound-defined active synovitis exhibit higher disease activity and increased serum levels of angiogenic biomarkers, Arthritis Research & Therapy 2014, 16:R5

Acknowledgements This paper is partially supported by the Sectoral Operational Programme Human Resources Development (SOP HRD), financed from the European Social Fund POSDRU/159/1.5/S/137390.

Disclosure of Interest None declared