Clinical Utility and Accuracy of Point-of-Care Testing for Anti-TNF Drug Monitoring and Loss of Response.

Background And Aims: Point-of-care tests (POCT) enable immediate measurement of anti-TNF blood concentrations. This study examined the association between loss of response (LOR) to infliximab (IFX) or adalimumab (ADL) and serum concentrations measured with POCT and enzyme-linked immunosorbent assay (ELISA) in inflammatory bowel disease (IBD) patients.

Methods: Patients with IBD with stored IFX or ADL serum samples were recruited. POCT was conducted, agreement with ELISA was evaluated using Bland-Altman plots. The primary endpoint was LOR defined as change in therapy, IBD-related surgery, new actively draining fistula, and/or endoscopic deterioration. ROC curves and quartile analysis assessed the association between concentrations and LOR.

Results: A total of 176 patients were included (92 IFX/84 ADL, 154 Crohn's disease, and 22 ulcerative colitis). Median follow-up time was 20 months (interquartile range 9-38). LOR occurred in 37/84 (44%) ADL users and 55/92 (60%) IFX users. Median serum concentrations were significantly lower in LOR patients compared with sustained response, measured by both techniques for ADL (POCT: 6.45 vs 13.48 µg/mL, P <.001; ELISA: 4.80 vs 8.80 µg/mL, P <.001) and IFX (POCT: 2.39 vs 6.50 µg/mL, P <.001; ELISA: 1.70 vs 4.40 µg/mL, P <.001). Quartile analysis revealed that higher serum concentrations were associated with maintained response. ROC curve analysis demonstrated good or excellent discrimination for POCT and ELISA in association with LOR (AUC IFX: POCT = 0.82, ELISA = 0.76; AUC ADL: POCT = 0.82, ELISA = 0.81; all P <.0001). An overestimation of serum concentrations with POCT was observed.

Conclusions: Serum ADL and IFX POCT concentrations are comparable to ELISA and associated with LOR, indicating its clinical utility.