TNF and rheumatoid arthritis: Based on diagnosis and ongoing anti-rheumatic treatments patients were stratified into the following groups: 1) RA on MTX (n = 50); 2) RA on anti-TNF as monotherapy (n = 38); 3) RA on anti-TNF + MTX (n = 53); 4) RA on other biologics (abatacept (n = 5), rituximab (n = 10), tocilizumab (n = 2)); 5) SpA on anti-TNF as monotherapy (n = 41); 6) SpA on anti-TNF + MTX (n = 51); and 7) SpA on NSAIDs/analgesics (controls, n = 41).