Discordant inflammation and pain in early and established rheumatoid arthritis: Latent Class Analysis of Early Rheumatoid Arthritis Network and British Society for Rheumatology Biologics Register data

McWilliams, Daniel F.; Ferguson, Eamonn; Young, Adam; Kiely, Patrick D.W.; Walsh, David A.

Abstract

Background
Rheumatoid arthritis (RA) disease activity is often measured using the 28 joint Disease Activity Score (DAS28). We aimed to identify and independently verify subgroups of people with RA that may be discordant with respect to self-reported and objective disease state, with potentially different clinical needs.

Methods
Data were from 3 cohorts; (1) Early RA Network (ERAN), and the British Society for Rheumatology Biologics Register (BSRBR) (2) commencing TNF-α inhibitors or (3) using non-biologic drugs. Latent Class Analysis (LCA) used variables related to pain, central pain mechanisms or inflammation (pain, vitality, mental health, erythrocyte sedimentation rate (ESR), swollen joint count (SJC), tender joint count (TJC), visual analogue scale-general health (VAS)). Clinically relevant outcomes were examined.

Results
Five, 4 and 4 latent classes were found respectively in ERAN, BSRBR TNF-inhibitor and non-biologic cohorts. The proportion of people assigned with >80% probability into latent classes were 76%, 58% and 72% in ERAN, the TNF-inhibitor and non-biologic cohorts respectively. The latent classes displayed either concordance between measures indicative of mild, moderate or severe disease activity; discordantly worse patient-reported measures despite less markedly elevated inflammation; or discordantly less severe patient-reported measures despite elevated inflammation. Latent classes with discordantly worse patient-reported measures represented 12%, 40% and 21% of the ERAN, TNF-inhibitor and non-biologic cohorts respectively, contained more females, and showed worse function. In those latent classes with worse scores at baseline, DAS28 and function improved over 1 year (p<0.001 for all comparisons), and scores differed less at follow up than at baseline.

Discussion
Discordant latent classes can be identified in people with RA, and these findings are robust across 3 cohorts with varying disease duration and activity. These findings could be utilised to identify a sizeable subgroup of people with RA that might gain added benefit from pain management strategies.

Citation

McWilliams, D. F., Ferguson, E., Young, A., Kiely, P. D., & Walsh, D. A. (2016). Discordant inflammation and pain in early and established rheumatoid arthritis: Latent Class Analysis of Early Rheumatoid Arthritis Network and British Society for Rheumatology Biologics Register data. Arthritis Research and Therapy, 18(1), Article 295. https://doi.org/10.1186/s13075-016-1186-8

• Journal Article Type: Article
• Acceptance Date: Nov 17, 2016
• Online Publication Date: Dec 13, 2016
• Publication Date: Dec 13, 2016
• Deposit Date: Dec 12, 2016
• Publicly Available Date: Dec 13, 2016
• Journal: Arthritis Research and Therapy
• Print ISSN: 1478-6354
• Electronic ISSN: 1478-6362
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 18
• Issue: 1
• Article Number: 295
• DOI: https://doi.org/10.1186/s13075-016-1186-8
• Keywords: Rheumatoid arthritis – Pain – Inflammation – Latent class analysis
• Public URL: https://nottingham-repository.worktribe.com/output/833817
• Publisher URL: http://arthritis-research.biomedcentral.com/articles/10.1186/s13075-016-1186-8
• Contract Date: Dec 12, 2016