3. Therapeutical effect: we will calculate the retention rate over time, and will compare the changes in different variables in the group of patients who have received TNF blockers monotherapy matched (using a propensity score) to 1,2 or 3 patients who have received TNF blockers in combination with synthetic DMARDs. We will assess and compare DAS28 and HAQ at short term (after at least 8 weeks of treatment) and long term (last available visit) in groups. The structural efficacy was evaluated by the radiographic progression at last available visit. We will identically estimate the drug effect depending on the TNF blocker used, by calculating the retention rate and comparing DAS28 at short term and long term.