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

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.

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.

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.

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