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Predictors for low disease activity and remission in rheumatoid arthritis patients treated with biological DMARDs.

BACKGROUND
Optimal outcome of treatment in rheumatoid arthritis (RA) is early clinical remission to delay joint damage. Therefore, severe RA patients with inadequate response to conventional disease modifying anti-rheumatic drugs (cDMARDs) need highpotency drug as biological DM4RDs (bDMARDs). In general, one-third of RA patient could not get into disease remission with cDMARDs, and half ofthem are still suffering from severe arthritis. However, high cost of this agent is the major barrier for patient engagement, and it is affordable to only 5-10% of patients. We need a good strategy to distribute bDMARDs to patients, especially in limited resource situation.


OBJECTIVE
We explored the characteristics ofRA patients who were currently using biologic agents in Ramathibodi Hospital to determine the favorable treatment outcome.


MATERIAL AND METHOD
The studied patients were RA patients classified according to ACR/EULAR 2010 criteria and using any biologic agents, between 2010 and2012. Demographic data and treatment outcome (low disease activity and remission) were retrievedfrom patient records. Univariate analysis and generalized estimating equation (GEE) were used to analyze predicting factors to control disease at one year. Kaplan-Meier and log rank test were used to analyze time to disease remission or low disease activity.


RESULTS
Patients treated with bDMARDs in Ramathibodi Hospital demonstrated long disease duration (mean 130.7 months) and severe disease activity (mean DAS28 5.37). At 1-year after treatment, 19.4% and 12.9% ofpatients achieved low disease activity (low DAS) and disease remission, respectively. At 3-years after treatment, 88.9% and 45.2% of patients attained low DAS and remission. Patients who started bDMARDs after 2010 had significantly shorter time to control disease when compared to patients who started bDMARDs before 2010 (10 months vs. 34 months). Moreover, we observed that patient who started bDMARDs after 2010 using more cDMARDs (2.5 vs. 1.7, p = 0.02) and higher dose of methotrexate (10.7 vs. 6.5, p = 0.03). There were no association between disease control status and treatment (methotrexate, prednisolone, biologic agent) or disease duration. However the exposedstatus ofbiologic agent was associated with low DAS or remission at the first year of observation (p = 0.004 and 0.04, respectively).


CONCLUSION
Chance to control rheumatoid arthritis in the level of remission or low disease activity is predicted by time of bDAMRDs exposure. This result is mainly influenced by dose ofmethotrexate and number of cDMARDs.