TNF and rheumatoid arthritis: aP = 0.003 compared to RA on MTX; P = 0.033 compared to RA on anti-TNF monotherapy; P = 0.001 compared to RA on anti-TNF + MTX; P = 0.005 compared to SpA on antiTNF + MTX; bP = 0.039 versus RA on anti-TNF monotherapy (Chi2 test).