We investigated associations at baseline and during tocilizumab treatment among haemoglobin , parameters of haemoglobin and iron homeostasis [ ferritin , total iron-binding capacity ( TIBC ) , hepcidin , haptoglobin ] , IL-6 and acute-phase reactants [ C-reactive protein ( CRP ) , erythrocyte sedimentation rate ( ESR ) ] to identify statistical correlates of rise in haemoglobin level .