Lateral flow test versus enzyme‐linked immunosorbent assay to measure infliximab trough concentrations: A head‐to‐head comparison

Abstract Objectives Infliximab is an antitumour necrosis factor agent used to treat inflammatory bowel disease (IBD). Measurement of infliximab trough concentrations (C‐troughs) are used to optimize drug exposure and improve outcomes. Currently, enzyme‐linked immunosorbent assays (ELISAs) are used predominantly for this purpose. Novel lateral flow immunoassays provide a rapid result. Methods We collected 100 paired serum samples of adolescents and young adults with IBD, who were treated with infliximab maintenance infusions. C‐troughs were measured with the Quantum Blue® lateral flow test (QB) with ELISA. Results were categorized as low‐range (mean C‐trough ≤5 µg/mL) or high‐range (>5 µg/mL). A Bland–Altman plot was created with limits of clinical acceptability set at ≤2 µg/mL for low‐range and ≤40% for high‐range C‐troughs. A concordance matrix was created to evaluate the C‐trough‐based clinical scenario (whether or not to escalate infliximab) using a cutoff value of 5 µg/mL. Results Agreement between QB and ELISA was good (intraclass correlation coefficient: 0.85). In the low‐range, 90% (95% confidence interval [CI]: 79–96) of measurements were within the limits of clinical acceptability. In the high‐range this was 67% (95% CI: 53–79). QB provided higher results than ELISA. The concordance matrix showed 81% agreement (95% CI: 72–88, κ : 0.62). Conclusions Lateral flow‐ and ELISA‐based infliximab C‐trough measurements were in agreement. The swift establishment of infliximab C‐troughs matters for patients experiencing increased disease activity. In the event of a low C‐trough, prompt dose escalation can be initiated.