Background/Purpose: Randomized clinical trials in RA have until recently focused on patients (pts) with high disease activity, but the majority of pts in the clinic have moderate disease activity. A specified threshold of disease activity for institution of TNF inhibitors (TNFi) has not been mandatory in Norwegian health care, thus pts with low or moderate disease activity have gained access to these therapies. Our objective was to assess what proportion of pts starting TNFi therapy had moderate disease activity at baseline, and to compare the outcomes in these pts to those with high disease activity.

Methods: Data for this study were provided by NOR-DMARD – a Norwegian multicentre, longitudinal observational study of consecutive pts with arthritides starting new DMARD regimens. The current analyses included biologics naïve pts with moderate (DAS28 3.2-5.1) or high (DAS28 >5.1) baseline disease activity who started treatment with TNFi + methotrexate (MTX). Baseline characteristics, utility gains (SF-6D and EQ-5D), ACR responses as well as remission rates at 3 and 6 months were compared by Chi² test, two-samples t test and Mann-Whitney U test as appropriate. 2-yr drug survival was compared by Kaplan-Meier analysis with log-rank test.

Results: The study included 296 pts with moderate (DAS28 3.2-5.1) and 347 pts with high (DAS28 >5.1) disease activity. 73 pts with DAS28 ≤3.2 at baseline were excluded. Mean(SD) DAS28 were 4.30(0.49) vs. 6.18(0.76), respectively. Overall, 73% were female, mean/median disease duration was 9.2/5.4 years, 75% were rheumatoid factor positive and 30% current smokers (no significant differences between the groups). The pts with moderate disease activity were significantly younger (mean 52 vs. 54 years, p=0.03) and had better baseline scores for 28-SJC, 28-TJC, patient and physician global, CRP, ESR, pain VAS and fatigue VAS (all p<0.001). Further, mean(SD) MHAQ scores were 0.57(0.41) vs. 0.97(0.52), SF-6D 0.62(0.11) vs. 0.54(0.11), and EQ-5D 0.56(0.28) vs. 0.32(0.31) in the moderate vs. high disease activity group (all p<0.001). Three- and 6-month utility gains were significantly larger in the high disease activity group while there were no statistically significant differences in ACR responses (table). As expected, remission rates were significantly higher in the moderate disease activity group (table). 2-yr drug survival was similar in the 2 groups (estimated 57% vs. 56%, p=0.42) and reasons for discontinuation were also similar.

Conclusion: Of biologics naïve pts starting TNFi + MTX, 52% had a baseline DAS28 <5.1. Pts with moderate disease activity when starting their first TNFi achieved higher remission rates but lower utility gains than pts with high disease activity, while ACR responses and drug survival were similar. Such comparisons can provide information for cost-effectiveness analyses which are increasingly important and necessary to guide decision making in this field.