Racial origin and its effect on disease expression and HLA‐DRB1 types in patients with rheumatoid arthritis: a matched cross‐sectional study

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Abstract
Objective. There are a significant number of patients with rheumatoid arthritis (RA) of North Indian or Pakistani origin (Asian) now living in the UK. RA has been poorly studied in this racial group. The aim of this study was to compare RA in this Asian group with RA in the indigenous northern European (European) population. It was hypothesized that these two racial groups would have different disease expressions and immunogenetics that could be relevant to pathogenesis, prognosis and therapy. Methods. One hundred and seven Asian RA patients, who fulfilled the 1987 American College of Rheumatology criteria, were stringently matched for age, sex and disease duration with 107 European RA patients, and were fully assessed. Results. The Asian RA patients had significantly fewer bony erosions [median Larsen score 58.5 (interquartile range 45.5–77.8) vs 68 (52–93) for European patients; P = 0.0066, Mann–Whitney U‐test] and rarely had nodules (5.7 vs 20%, P = 0.0019, Fisher's exact test). The two groups had the same prevalence of rheumatoid factor positivity, number of swollen joints and level of inflammation (C‐reactive protein). The Asian RA patients had a reduced prevalence of the conserved third allelic hypervariable region (3AHVR) (45 vs 82%, P < 0.0001, Fisher's exact test), particularly DRB1*0401 (4.5 vs 55%). However, the prevalence of the conserved 3AHVR was significantly increased in the Asian RA patients compared with Asian controls. By contrast, the Asian patients had more tender joints [13.5 (7–22) vs 5.5 (2–11.8); P < 0.0001 Mann–Whitney U‐test]. The Health Assessment Questionnaire score was also significantly worse in the Asians compared with the Europeans [median 2.0 (1.13–2.63) vs 1.25 (0.5–2.13), P = 0.0001). Conclusions. The Asian patients had similar levels of inflammation and less damage but more pain and disability than the matched European RA patients. Of the known prognostic factors for erosions (rheumatoid factor, conserved 3AHVR, swollen joints and C‐reactive protein), only the conserved 3AHVR was reduced in the Asian RA patients, and this was consistent with their less erosive disease. These data also indicate the importance of pain as well as erosive damage in determining disability in Asian patients and stress the importance of adequate pain relief, in addition to disease suppression, when treating Asian RA patients.