AB1264 Barriers against testing anti-tnf drug levels and anti-drug antibodies in routine clinical practice
Authors: S.P. Gavan, G. Daker-White, K. Payne, A. Barton
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> There is growing interest in using tests to measure anti-TNF drug levels and anti-drug antibodies (ADAb) in routine clinical practice for patients with rheumatic diseases. Testing may provide rheumatologists with additional information when considering a decision to adjust biologic treatment; for example, a decision to increase the interval between injections of an anti-TNF or to change treatment to a biologic that has a different target. However, it is not clear whether rheumatologists consider drug level and ADAb testing to be a useful technology within their routine clinical decision-making. Testing may be implemented imperfectly if rheumatologists perceive barriers against measuring drug levels and ADAb which, in turn, can affect the effectiveness and cost-effectiveness of care. <h3>Objectives</h3> To explore the potential barriers against testing anti-TNF drug levels and ADAb in routine clinical practice. <h3>Methods</h3> Semi-structured telephone interviews were conducted individually with a purposive sample of consultant rheumatologists from different hospitals across England. The telephone interviews were recorded and transcribed verbatim. Pilot interviews were undertaken to develop the interview schedule. The rheumatologists were invited to discuss their perceptions and experiences of anti-TNF drug level and ADAb testing within their own clinical practice. The transcripts were analysed by thematic framework analysis where themes comprised perceived barriers to testing. Ethical approval was obtained from The University of Manchester's Research Ethics Committee. <h3>Results</h3> Eleven rheumatologists provided informed consent to participate in the study. All rheumatologists demonstrated an awareness of tests that were available to measure anti-TNF drug levels and ADAb. However, the majority (n=10) did not use these tests in their routine clinical decision-making. Five potential barriers against testing were identified as themes:<sup>1</sup> recognising the clinical problem within their own patients;<sup>2</sup> understanding the purpose of testing drug levels and ADAb,<sup>3</sup> a lack of robust evidence to support testing,<sup>4</sup> insufficient capacity to implement testing locally, and<sup>5</sup> the additional cost associated with testing. <h3>Conclusions</h3> The potential barriers against measuring anti-TNF drug levels and ADAb suggest that introducing these tests into practice for rheumatology may be challenging. Authoritative guidance for measuring anti-TNF drug levels and ADAb in specific rheumatic diseases may reduce the uncertainty over the purpose of testing in routine clinical settings. The generation and dissemination of robust evidence for the accuracy, effectiveness, and cost-effectiveness of testing is likely to be informative to rheumatologists and decision-makers that allocate resources for health care. Decisions to introduce testing in clinical practice may benefit from considering the implications of capacity constraints when analysing samples and the mechanisms to pay for the additional cost of testing. These barriers against testing are not unique to the health care system in England and may generalise to the delivery of care for rheumatic diseases within health care systems internationally. <h3>Disclosure of Interest</h3> None declared