Performance of Remsima® Monitor Drug Level versus RIDASCREEN IFX Monitoring in therapeutic drug monitoring of infliximab in patients with inflammatory bowel disease: A study of diagnostic accuracy

Therapeutic drug monitoring (TDM) is effective in optimizing the efficacy of infliximab in patients with inflammatory bowel disease (IBD). An affordable way of monitoring is in high demand. This study evaluated the analytical and clinical performances of the newly available Remsima monitor kits and compared them with the established enzyme-linked immunosorbent assay kits. The trough level of infliximab in patients with IBD treated with an infliximab originator (Remicade) or biosimilar compounds (Remsima and Remaloce) was measured using a Remsima® Monitor Drug Level (Remsima) kit at the Samsung Medical Center, Seoul, Korea. Twenty-six plasma samples were collected immediately before the infusion of infliximab from 18 patients with IBD (Remicade, n = 8; Remsima, n = 6; and Remaloce, n = 4). The intra-assay intraclass correlation coefficient (ICC) of the RIDA and Remsima kits was 0.951 (95% CI = 0.908–0.976) and 0.990 (95% CI = 0.981–0.995). The inter-assay ICC of infliximab trough level between the RIDA and Remsima kits was very high (R = 0.971; 95% CI = 0.935–0.987), and the mean difference between the kits was 1.458 (95% limits of agreement = −3.302 to 6.219). The intra- and inter-assay reliabilities of all types of infliximab did not show significant differences. Qualitative stratification revealed substantial similarities between the kits (weighted kappa = 0.798). This study indicated that the Remsima kit was reproducible and highly correlated with the RIDA kit.