Acknowledgements
This work was supported by two grants (CM/09/08 and CM/06/08) from the CajaMurcia Foundation, Murcia Region, Spain. PCZ is contracted by the Health Research Fund, Council of Healthcare, Murcia Region, Spain. We are grateful to the personnel at the Day Hospital and the Rheumatology Department from HUSMR for their help in carrying out this study, to F J Orantes-Casado for his help in the statistical analysis, and to D Arcas for reviewing the English version of this manuscript.