A nationwide survey on therapeutic drug monitoring of anti-tumour necrosis factor agents for inflammatory bowel disease

Background Routine therapeutic drug monitoring (TDM) during treatment with anti-tumour necrosis factor (anti-TNF) agents in inflammatory bowel disease may increase treatment efficacy and cost-effectiveness, and reduce the risk of loss of response. Aims To assess the current use of anti-TNF agent TDM, including trough concentration and anti-drug antibodies, among gastroenterology practitioners in New Zealand. Methods A web-based survey was delivered to gastroenterologists and advanced trainees in New Zealand, identified by the New Zealand Society of Gastroenterology. Results The response rate was 36% (48/134). Adalimumab was the most common initial anti-TNF agent used (78%, infliximab 22%). Ninety-three percent of those who completed the survey used TDM, mainly in cases of non-response or loss or response. Most respondents (93% and 83% for adalimumab and infliximab, respectively) measured trough concentrations within 24 h prior to the next administration. In patients in clinical remission but with endoscopic inflammation on anti-TNF agents, 72% would measure drug concentrations. In the presence of anti-drug antibodies, 45% would add an immunomodulator in patients with active disease and 47% would add an immunomodulator in patients in remission. With low trough concentrations, 77% would make no changes if the patient was in remission, and 75% would increase the dose in case of active disease. Conclusion TDM was routinely used among inflammatory bowel disease gastroenterology clinicians who responded to this survey. However, interpretation of results and decision-making is variable, suggesting more guidance is required.