THU0068 Absolute Monocyte Counts Are Associated with Adverse EULAR Response after 6 Months of Treatment with A Biologic Agent for Rheumatoid Arthritis
Authors: S.F. Ling, K. Stylianou, P. Ho, M. Bukhari, D. Plant, A. Barton
Journal: Annals of the Rheumatic Diseases (2016)

<h3>Background</h3> Absolute monocyte counts after 3 months of treatment have been found to be predictive of clinical response to adalimumab at 6 months in rheumatoid arthritis (RA) patients<sup>1</sup>. It has also been shown that resistance to spontaneous apoptosis of monocytes <i>in vitro</i> predicts inadequate response to etanercept<sup>2</sup>. We hypothesise that absolute monocyte counts obtained from routine pre-treatment blood testing has predictive utility for treatment response to biologic agents. <h3>Objectives</h3> To assess whether monocytes and other white blood cell subtypes are associated with treatment response at 6 months in RA patients. <h3>Methods</h3> Full blood count (FBC) data was collected from patients attending 2 centres participating in the Biologics in RA Genetics and Genomics Study Syndicate (BRAGGSS), Manchester Royal Infirmary and Royal Lancaster Infirmary, from 2009–2015. BRAGGSS is a UK-based multi-centre inception cohort of secondary-care RA patients. Spearman correlation was carried out to explore relationships between pre-biologic differential white cell count (WCC) and absolute DAS28 (and its components) at treatment start (baseline) and 6 months. Logistic regression was used to explore associations between differential WCC and EULAR response at 6 months. Stata v13.1 was used for all statistical analyses. <h3>Results</h3> 130 patients had WCC data available for analysis. They all satisfied American College of Rheumatology 1987 classification criteria for RA. 104 patients (80%) were female, with a mean age of 56.21 (SD 13.07). Mean baseline DAS28 score was 5.96 (SD 0.92) and mean monocyte count at baseline was 0.62*10<sup>9</sup>/L (SD 0.22). Patients were on a variety of biologics: etanercept (n=56), adalimumab (n=24), rituximab (n=13), abatacept (n=10), golimumab (n=5), tocilizumab (n=12) and certolizumab (n=10). Pre-treatment monocyte count was not associated with DAS28 at baseline, but correlated with DAS28 at 6 months (rho=0.19, p=0.028). When a cut-off of 0.62*10<sup>9</sup>/L was used, high monocyte count was associated with DAS28&gt;3.2 at 6 months (OR1.72 [95% CI 1.12–2.64], p=0.013), and with poor EULAR response (OR 2.82 [95% CI 1.12–7.13], p=0.028). Neutrophil count was associated with DAS28 at both baseline (rho=0.22, p=0.013) and 6 months (rho=0.21, p=0.019). Neutrophil count was significantly associated with reduced odds of achieving a good EULAR response at 6 months (OR 0.82 [95% CI 0.69, 0.96], p=0.017). These neutrophil counts likely reflect ongoing inflammation, contributing to poor response to biologic therapy<sup>3</sup>. <h3>Conclusions</h3> Monocyte counts were associated with increased DAS28 at 6 months, but not baseline, and with poor EULAR response at 6 months. This could provide a useful and widely available predictive biomarker, as FBC is routinely carried out in all patients commencing disease-modifying therapy in the UK. In future, monocyte count at baseline may be used to predict treatment response to biologics in RA patients at 6 months. Further studies with increased sample size are required to confirm these findings. <h3>References</h3> Chara L et al. Arthritis Res Ther 2012;14:R175. Meusch U et al. Arthritis Res Ther 2013;15:R219. Wright HL et al. Nat Rev Rheumatol 2014;10:593–601. <h3>Disclosure of Interest</h3> None declared