GASTROENTEROLOGY
laboratories may employ various analysers and assay formulations, leading to inconsistent results that can vary significantly across testing facilities. These inconsistencies make it challenging for clinicians to interpret results with confidence, particularly when the data from different labs aren’t directly comparable. Although the introduction of World Health Organization (WHO) standard materials has improved overall test consistency, notable discrepancies remain. Much of this challenge stems from ADA monitoring.
ADA tests come in two primary
Gastrointestinal disorders are increasingly recognised as a global health challenge, with rising incidence rates and substantial implications for the general population, with over half a million people in the UK alone living with Crohn’s disease and ulcerative colitis.
biologic therapies.16 This reactive tactic
can help clinicians to tailor therapy based on individual patient needs; low drug levels without antibodies may indicate a need for a higher treatment dose, while low drug levels with high ADA levels may direct clinicians to administer a different biologic or add immunosuppressants to the treatment regime.17 In addition to its reactive use, TDM can be applied proactively through regular measurement of drug and ADA levels, even before any clinical signs of drug unresponsiveness or LOR appear. This proactive approach offers notable advantages: it reduces adverse effects by preventing unnecessary dose escalations, improves patient outcomes by sustaining the therapeutic efficacy of TNF-α inhibitors, and lowers healthcare costs by extending the effective lifespan of these biologics. Preliminary data suggests that proactive TDM may outperform empirical dose optimisation and reactive
TDM,18-20 promoting higher rates of
mucosal healing and lowering the risk of hospitalisations and treatment failures.17,21
Limitations and levers for implementing proactive TDM Proactive TDM has demonstrated clear potential for enabling timely interventions and improving patient outcomes in IBD care, yet its adoption among clinicians remains limited. Currently, only 54% of clinicians take advantage of proactive TDM in their practice.16
formulations: drug-sensitive assays – which detect free antibodies that are not bound to circulating drug – and drug- tolerant assays, which incorporate an acid dissociation step to release ADAs from bound drug to detect total ADAs in the serum, regardless of circulating drug levels.23
Each assay type offers
distinct advantages for specific clinical needs; for instance, drug-sensitive assays are particularly effective for reactive monitoring, as they identify antibodies only after a substantial immune response has begun. In contrast, drug-tolerant assays offer a broader measurement, allowing clinicians to capture all ADAs in the serum, and potentially identify issues related to immunogenicity at an earlier stage. However, interpreting results can be complex for both assay types, and greater knowledge among clinicians is essential to interpret and apply results optimally, ensuring the best outcomes for patient care.
This modest uptake is partly
due to its recent emergence in the standard of care for IBD, meaning that many healthcare professionals have had limited exposure to its benefits and practical applications.
Challenges in testing A major hurdle in implementing TDM overall is the variability in laboratory testing methods and results.22
Different
Lack of endorsement Compounding these challenges is the absence of formal endorsement from influential gastroenterology organisations. Although NHS Scotland has led the way by introducing a centrally funded TDM service supporting both proactive and reactive testing,24 this model has yet to gain official support from the British Society of
WWW.PATHOLOGYINPRACTICE.COM MAY 2025
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AdobeStokc / Sebastian Kaulitzki
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