ADA and rheumatoid arthritis: Therapeutic decision-making within RA does not include routine monitoring of ADAs or drug concentrations in patient serum.1 However, therapeutic drug monitoring may be considered to aid cycling or swapping decisions.79 For those patients who report loss of response, therapeutic drug monitoring may help to identify those patients who are more likely to benefit from cycling within class.80 High drug levels and absence of ADA would suggest that switching to an alternative MoA would be advisable, whereas low drug levels and high ADA would suggest switching within class.