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SAT0385 Is interleukine-6 a better surrogate biomarker of persistent joint inflammation than C-reactive protein in early arthritis? Results from the espoir cohort
  1. A. Baillet1,
  2. L. Gossec2,
  3. S. Paternotte2,
  4. N. Hoyle3,
  5. B. Combe4,
  6. O. Meyer5,
  7. M. Dougados2
  1. 1Hôpital Sud Chu Grenoble, Echirolles
  2. 2Rheumatology B, Cochin Hospital, Paris, France
  3. 3Roche Diagnostics GmbH, Penzberg, Germany
  4. 4Lapeyronie Hospital, Montpellier
  5. 5Bichat Hospital, Paris, France

Abstract

Background Interleukin-6 (IL-6) is one of the most important cytokines in rheumatoid arthritis (RA). IL-6, mainly produced in the inflammed joint, is involved in several features of structural damage. Although some authors suggested that IL-6 assessment may improve RA management, data is scarce in early arthritis

Objectives To determine whether IL-6 could be used to assess disease activity and structural damage in early arthritis. For this, we assessed the relationship between IL-6, CRP as a comparator, and several outcome measures during the first 36 months of an early arthritis cohort

Methods The early arthritis cohort ESPOIR is a French national observational cohort of patients with at least 2 joints affected by synovitis for >6 wks and <6 months at baseline. IL-6 was assessed at each timepoint from frozen sera using a chemiluminescence assay (Elecsys® IL-6, Roche Diagnostics). Thus, IL-6 and CRP were compared to repeated measurements through 36 months of inflammation (i.e. swollen joint count (SJC) and ESR-DAS28), function assessed by HAQ and radiographic severity by Total Sharp van der Heijde score (SHS). Progressors were defined as patients with a change of SHS >1 at 12 months. The hypothesis was that IL-6 at baseline and through follow-up would be better correlated than CRP to radiographic change and to persistent synovitis. To further assess the relationship between IL-6 and inflammation, the presence and the grade of synovitis was recorded in a sample of 126 patients of the cohort using ultrasonography (US). Last Observation Carried Forward imputation method was used. The relationship between the IL-6 level either at baseline or over time (AUC IL-6), CRP, and the above mentioned parameters was investigated by Spearman’s rank test

Results 812 patients of the 813 patients in the cohort had IL-6 levels. Of these 812 patients, 623 (76.7%) were female, mean (SD) age was 48.1 (12.5) years, and mean duration of joint swelling was 4.8 (5.8) months; 579 patients (71.3%) satisfied the ACR 1987 criteria for RA at baseline. Baseline IL-6 was 25.5 (59.0) pg/ml and was significantly higher in early RA (30.9 (67.6) pg/ml) than in early undifferenciated arthritis (12.2 (23.1) pg/ml, p<0.0001). IL-6 was twice higher in the 447 progressors (31.1 (75.0) vs. 15.0 (23.2), p<0.0001). The variation through follow-up of both IL-6 and CRP moderately correlated with the variation of HAQ (respectively r=0.220 and r=0.214, both p<0.0001) and with the change of ESR-DAS28 (r=0.279 and r=0.268, both p<0.0001). Variation of SJC was more correlated with variation of IL-6 (r=0.382, p<0.0001) than with variation of CRP (r=0.159, p<0.0001). SHS change was more associated with variation of IL-6 (r=0.330, p<0.0001) than with variation of CRP (r=0.077, p=0.031). At baseline, IL-6 significantly correlated with the number of US synovitis ((r=0.198, p=0.025 in B mode, r=0.259, p=0.003 in Doppler mode) while the correlation was not significant with CRP (r=0.087, p=0.330 in B mode and r=0.066, p=0.462 in Doppler mode)

Conclusions IL-6 monitoring is correlated with persistent synovitis and should be considered as a surrogate marker of RA and structural damage in early arthritis.

Disclosure of Interest A. Baillet: None Declared, L. Gossec: None Declared, S. Paternotte: None Declared, N. Hoyle Employee of: Roche Diagnostics GmbH, B. Combe: None Declared, O. Meyer: None Declared, M. Dougados: None Declared

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