Background Research into the pathogenesis of rheumatoid arthritis (RA) has been focusing on identifying disease biomarkers that can predict response to therapy. Early work identified differing levels of pro-inflammatory cytokines within a cohort of RA patients . A recent study looking at the role of a modified release glucocorticoid preparation in the management of RA may have identified a distinct subgroup of patients who are resistant to therapy  with raised circulating levels of the cytokines TNF-α, IL-4, IL-1 receptor antagonist (IL-1ra) and IL-1β compared to treatment responders. The concept of glucocorticoid resistance in RA has been observed in other studies and across the spectrum of inflammatory disorders [3,4].
Objectives This study explores the the possibility of identifying a treatment resistant phenotype subset of patients with RA through peripheral serum cytokine measurements.
Methods 41 patients with RA were recruited from general rheumatology clinics in the South-West of the United Kingdom (Bristol and Plymouth). Additional exclusion criteria included active malignancy, active infection and co-existing auto-immune disease. Patient blood samples were taken in the morning to minimise diurnal cytokine variations and cytokine assays were performed using a MILLIPLEX® MAP multiplex assay kit at a commercial laboratory in Germany.
Results Results were analysed according to the number of patients who had raised serum TNF-α, IL-4, IL-1ra and IL-1β above the cohort median for each cytokine. The frequencies of the number of patients who had 0,1,2,3 or all 4 cytokines raised were recorded.
This revealed a biphasic distribution of patients with 16/41 patients having 3 or 4 raised cytokines versus 22/41 patients having only 1 or 0 cytokines raised. Only 3 patients had 2 raised cytokines. This is a much smaller figure than predicted, as we would expect the population to be normally distributed. The P value for the Chi squared test comparing the observed population versus the expected normal distribution was <0.0001.
Conclusions These results confirm previous observations that a distinct subset of patients with rheumatoid arthritis patients can be identified through the serum cytokine signature. Previous studies seem to imply that these patients may exhibit a glucocorticoid resistant phenotype. Further work is planned to explore the association of these two subsets of rheumatoid arthritis with various clinical characteristics.
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Disclosure of Interest None Declared
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