Minimal disease activity in early and longstanding rheumatoid arthritis

Background: Several indexes are available to measure disease activity in rheumatoid arthritis (RA). Since complete remission is still rare in RA, there is a need of an easy set of criteria capable of identifying the proportion of patients reaching a minimal residual disease activity (MDA). Objectives: To define the `minimal disease activity' using few parameters and to compare it with the criteria proposed by OMERACT (OMERACT-MDA) that evaluates 28 joints only. Methods: 369 patients with long standing RA (LSRA) were evaluated for clinical and laboratory parameters (tender and swollen joint counts, HAQ, DAS 28, DAS 44, ESR, CRP) and were divided in patients reaching or not remission following EULAR criteria (DAS<1.6) [1]. Using ROC curves in this population we obtained, for HAQ, SJC and ESR, cut-off good predictors of a DAS<1.6. Finally, we tested the combination of the three cut-offs to define `minimal disease activity' in a 112 LSRA cohort and in a 74 early RA (ERA) cohort, in comparison to OMERACT-MDA criteria [2] and EULAR remission criteria. Results: Predictors of a DAS<1.6 obtained from the analysis of the LSRA cohort were: a) ESR < 20 (sensibility 73%, sensitivity 54%), b) SJC ≤ 2 (out of 44 joints) (sensibility 92%, sensitivity 64%), c) HAQ ≤ 0.5 (sensibility 85%, sensitivity 69%). We defined these three parameters as GISEA-MDA and we consider a patient as having a minimal disease activity if he meets all the three criteria. Among the cohort of 112 subjects with LSRA, 16 (14.3%) reached EULAR criteria for remission (DAS 28 <2.6), 10 (8.9%) satisfied the OMERACT criteria for MDA and 23 (20.5%) fulfilled the GISEA-MDA criteria. All the patients satisfying EULAR remission and OMERACT-MDA criteria (16 and 10 subjects, respectively) were included in the group of 23 patients reaching the GISEA-MDA. No significant differences were observed for ESR, CRP, TJC, SJC, DAS and HAQ in the two subgroups of patients with OMERACT and GISEA-MDA. In the ERA population, 24 of the 74 patients (32.4%) achieved EULAR remission criteria, 30 (40.5%) the OMERACT-MDA and 30 (40.5%) the GISEA-MDA. Eighteen (75%) patients in EULAR remission and 24 (80%) in OMERACT-MDA were comprised in the last group. No differences were observed between the subgroups in clinical and laboratory parameters. Conclusion: Three simple parameters (HAQ, SJC assessed on 44 joints and ESR) seem to allow a valid index to identify RA patients with a minimal residual disease activity, with results comparable to criteria available at present. The GISEA-MDA criteria seems to behave very similarly to OMERACT criteria. References: 1. van Gestel AM, Previo ML, van Rijswijk MH, van de Putte LB, van Riel PL. Development and validation of the European League Against Rheumatism response criteria for rheumatoid arthritis. Comparison with the preliminary American College of Rheumatology and the WHO/International League Against Rheumatism Criteria. Arthritis Rheum. 1996 Jan;39(1):34-40. 2. Wells GA, Boers M, Shea B, Brooks PM, Simon LS, Strand CV et al. Minimal disease activity for rheumatoid arthritis: a preliminary definition. J Rheumatol. 2005 Oct;32(10):2016-24.