Background Both environmental or lifestyle factors, including smoking, overweight and periodontal disease, were found to be associated with an increased risk for developing rheumatoid arthritis (RA). Few studies suggested that blood transfusions (BT) could be another potential risk factor for RA. Although the underlying pathophysiological mechanism is unclear, it is well known that BT leads to significant modifications in recipient immune system.

Objectives The aim of this study was to estimate the prevalence of BT history in a cohort of patients with early RA, and to compare the course of the disease between transfused and non-transfused RA patients in the cohort.

Methods The ESPOIR cohort is a French national prospective cohort that included patients with early arthritis prone to develop into RA. History of BT before inclusion in the cohort was searched for each patient with a confirmed diagnosis of RA after five-year follow-up in the cohort.

A standardized prevalence ratio (SPR) was determined to evaluate the over-risk of BT past history in RA patients compared to age and sex matched general population. Clinical characteristics of RA were compared at inclusion and after five years of follow-up between BT recipients and non-recipients.

Results Among the 813 patients included in the cohort, 705 had a confirmed diagnosis of RA after five years of follow-up. Among assessable patients, 10.5% (72/686) had a past history of BT at inclusion in the cohort. For age and sex-matched general population, the prevalence of BT is about 0.3%, leading to a SPR of 35 (95%CI: 27.4 – 44). The median time between BT and onset of arthritis was 25.5 years (IQR: 16 – 33). Furthermore, patients with history of BT were preferentially ACPA-negative (75.0% [54/72] for BT recipients vs. 53.2% [327/614] for non-recipients; p<10^–4) and anti-DNA antibodies-negative (92.2% [59/64] for BT recipients vs. 81.3% [453/557] for non-recipients; p=0.03). At inclusion, BT recipients presented a significant higher activity of RA with a greater number of tender joints (11.7±7.9 vs. 9.0±7.0; p=3.10^–3) and a trend to a higher level of DAS28 score (5.5±1.3 vs. 5.2±1.1; p=0.08). This difference persisted after 5 years of follow-up with a greater number of tender joints (5.3±7.0 vs. 2.5±4.7; p=10^–4), a greater number of swollen joints count (2.0±3.8 vs. 1.1±2.4; p=0.02) and a higher level of DAS score (3.4±1.5 vs. 2.7±1.3; p=7.10^–4). Regarding the Sharp score, no significant difference was observed at inclusion (5.2±5.7 for BT recipients vs. 5.3±7.4 for non-recipients; p=0.89), and no excess variation was found for the two first years of follow-up (+ 4.9±6.0 for BT recipients vs. + 6.0±9.5 for non-recipients; p=0.37).

Conclusions This study suggests that BT could be a risk factor for developing RA, identified in about 10% of patients in the ESPOIR cohort. The long time between transfusion and disease onset may explain the discrepancies in older studies. Past history of BT is associated with an increased disease severity at onset and after 5-year outcome. Further studies are necessary to understand how BT is associated to subsequent RA.

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.1998