TNF and rheumatoid arthritis: In RA patients, there were no differences in levels of the three urinary cytokines according to age (≤60 versus >60 years), sex, disease duration (disease duration tertile) or use of medications, including prednisolone, methotrexate, leflunomide, hydroxychloroquine, or anti-TNF-α therapy as assessed by the Mann-Whitney U-test or the Kruskall-Wallis test (data not shown); the non-parametrical Kruskall-Wallis test was used to investigate the differences between more than two subgroups as obtained by categorization according to age or disease duration tertile.