Abstract Background In patients with inflammatory bowel disease (IBD) receiving anti-TNF therapy (aTNF), data suggest that reactive therapeutic drug monitoring (TDM) with medical optimisation improves rates of clinical remission.1 It is also cost-effective compared to empirical dose escalation.2 In our centre, Enzyme-Linked Immunosorbent Assay (ELISA) is the standard of care (SOC) alongside a drug-tolerant antibody (ab). Samples are sent externally, causing delays in reporting and clinical decision making. We aimed to externally validate the Biosynex point of care (POC) Analyzer® by correlating drug levels with SOC methods. We calculated the time to result. Methods We performed a prospective single-centre pilot study including patients with IBD on aTNF therapy (infliximab IFX or adalimumab ADA) where TDM was requested as SOC (project ID QI20867). We excluded patients receiving aTNF for non-IBD indications or those without disease activity (clinical, biochemical, radiological or endoscopic). Drug levels were assessed as per SOC and, simultaneously, via the Biosynex POC Analyzer®. POC drug ab levels used a drug-sensitive assay and were therefore compared descriptively. A Spearman’s rank-order correlation was used to assess the correlation between the SOC and POC aTNF level. Wilcoxon signed-rank test was conducted to compare the median time to result. Results At interim analysis, data for 27 patients receiving IFX (15 55%) or ADA (12 44% are available: 11 (40%) UC,15 (55%) CD, and 1 (3.7%) IBDU. Scatter plots correlating SOC and POC levels for IFX and ADA both demonstrate a linear relationship with strong positive correlations respectively; (df13) = 0.974, p 0.001, and (df10) = 0.970, p 0.001(Figure 1a,1b). The median time to result was 19 days (IQR 16-24) SOC compared with 1 day POC, P 0.001 (Table 1). The ab titre was not comparable given the different assays used. Neutralising antibodies were detected in 3 patients who had subtherapeutic drug levels 2.0units on POC testing. 2/3 cases also had positive SOC antibodies. 1 patient had a positive low titre POC ab but negative SOC ab. The remaining 4 patients with low titre SOC ab had POC drug level 2 so reflex testing was not performed . Conclusion TDM using the Biosynex POC Analyzer® appears to be reliable in terms of correlation of drug level titre with our SOC ELISA and may expedite and optimise clinical decision making in patients experiencing an IBD flare. We aim to complete our pilot study to gain more data and determine how expedited results may change clinical decision-making and affect long-term outcomes. More antibody data is required to draw conclusions. References: 1. Papamichael K, Afif W, Drobne D, et al. Therapeutic drug monitoring of biologics in inflammatory bowel disease: unmet needs and future perspectives. Lancet Gastroenterol Hepatol. Feb 2022;7(2):171-185. doi:10.1016/s2468-1253(21)00223-5 2. Steenholdt C, Brynskov J, Thomsen O, et al. Individualised therapy is more cost-effective than dose intensification in patients with Crohn’s disease who lose response to anti-TNF treatment: a randomised, controlled trial. Gut. Jun 2014;63(6):919-27. doi:10.1136/gutjnl-2013-305279 Conflict of interest: Dr. Affat, Azah: No conflict of interest Przemioslo, Robert: None Meade, Susanna: .Speaker fees FalkPharma, Abbvie Conference fees J&J, Advisory board J&J . Biosynex provided the point of care analyser and testing kits and that the analysis was performed independently
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