Objectives The aims of this study were to assess the association between area-level socio-economic deprivation and the phenotype of rheumatoid arthritis (RA), defined by rheumatoid factor (RF) and anticitrullinated peptide antibody (AC PA) status, and to determine whether any observed association can be explained by smoking.
Methods The authors performed logistic regression analysis of 6298 patients with RA, defined by American College of Rheumatology classification criteria modified for genetic studies. Analysis was stratified by cohort/recruitment centre. Socio-economic deprivation was measured using the Townsend Index.
Results Deprivation predicted RF but not ACPA positivity, independent of smoking. The ORs for trend across tertiles, adjusted for smoking, gender, period of birth and cohort/recruitment centre, were 1.14 (95% CI 1.01 to 1.29) for RF and 1.01 (95% CI 0.87 to 1.16) for ACPA. Even after adjusting for deprivation, smoking was strongly associated with ACPA positivity (OR 1.38, 95% CI 1.22 to 1.55). There was no evidence of any effect modification by the RA risk alleles (HLA-DRB1 shared epitope and PTPN22 rs2476601) that have previously been shown to modify the effect of smoking on ACPA and RF positivity.
Conclusions Among patients with RA, deprivation predicted RF positivity but not ACPA positivity. The effect of deprivation did not appear to be explained by smoking. Deprivation may be a marker for previously unrecognised, potentially modifiable environmental influences on the immunological phenotype of RA. Furthermore, given the known associations of RF positivity with prognosis and response to treatment in RA, these findings have potential implications for resource allocation and healthcare delivery.
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Collaborators YEAR consortium, BRAGGSS consortium, UKRAG consortium and ERAS consortium.
Funding This study was funded by the National Institute for Health Research-Leeds Musculoskeletal Biomedical Research Unit, Arthritis Research UK (grant numbers: 17552 (BRAGGSS), E0555 and 18066), Leeds Teaching Hospitals Charitable Trustees, Research and Development Support Fund for Guy's and St. Thomas' National Health Service Foundation Trust and the Lewisham Hospital National Health Service Trust. SLM holds a National Institute for Health Research Academic Clinical Lectureship.
Competing interests None.
Ethics approval The YEAR study was a multicentre collaboration across centres in Yorkshire and was approved by the Northern and Yorkshire REC (MREC 99/3/48). The BRAGGSS study was approved by the UK Central Office of Research Ethics Committees (COREC 04/Q1403/37). UKRAG was approved by the North West Multi-centre Research Ethics Committee (MREC 99/8/84). The ERAS is an inception cohort still in follow-up, which recruited patients between 1986 and 1998, from nine hospitals across England; ethical approval was gained from the East Hertfordshire Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.