4. Therapeutical effect:the retention rate over time will be calculated, the changes in different variables will be compared in the group of patients who have received TNF blockers matched (using a propensity score) to 1,2 or 3 patients who have not. The DAS28 and HAQ will be assessed and compared at the 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.The drug effect will be identically estimated depending on the TNF blocker used, by calculating the retention rate and comparing DAS28 at short term and long term.