Measurement of Anti-TNF Biologics in Serum Samples of Pediatric Patients: Comparison of Enzyme-Linked Immunosorbent Assay (ELISA) with a Rapid and Automated Fluorescence-Based Lateral Flow Immunoassay

Abstract

Background: Therapeutic drug monitoring (TDM) of infliximab (IFX) and adalimumab (ADL) mainly relies on the use of enzyme-linked immunosorbent assays (ELISA). More recently, rapid assays have been developed and validated to reduce turnaround time (TAT). Here, we compared IFX and ADL concentrations measured with both ELISA and a new fluorescence-based lateral flow immunoassay (AFIAS). Methods: In serum samples from pediatric patients, IFX and ADL drug levels, and total anti-IFX antibodies were measured using clinically validated ELISA kits (Immundiagnostik AG). Samples were further analyzed using a new rapid assay (AFIAS, Boditech Med Inc.) to measure drug levels and total anti-IFX antibodies. Results: Spearman's correlation coefficients (rho) were 0.98 [95% confidence interval (CI) 0.97 to 0.99] for IFX (p < 0.001) and 0.83 (95% CI 0.72 to 0.90) for ADL (p < 0.001). Calculated % bias was -14.09 (95% Limits of agreement, LoA, -52.83 to 24.66) for IFX and 15.79 (LoA -37.14 to 68.73) for ADL. For the evaluation of total anti-IFX antibodies, we did not collect sufficient data to establish a statistically significant correlation between AFIAS and ELISA. The inter-rater agreement showed a "substantial" and a "moderate" agreement for IFX and ADL, respectively. Conclusions: Our results show that the AFIAS assay has an accuracy and analytical performance comparable to that of the ELISA method used for TDM of IFX and ADL. Therefore, the introduction of this device into routine clinical practice could provide results more quickly and with similar accuracy as ELISA, allowing clinicians to rapidly formulate clinical decisions.

Keywords: anti-TNF biological agents; enzyme-linked immunosorbent assay (ELISA); fluorescence-based lateral flow immunoassay (AFIAS); pediatric patients; therapeutic drug monitoring (TDM); turnaround time (TAT).

Figure 1

Passing–Bablok correlations and Bland–Altman plots for infliximab (IFX) and adalimumab (ADL) drug levels. Passing–Bablok correlation plots for IFX (A) and ADL (B) drug levels. Continuous black and red lines indicate the linear and the Deming regression lines, respectively. The dotted blue lines indicate 95% confidence intervals (CIs). Bland–Altman plots of IFX (C) and ADL (D) drug levels. Continuous horizontal blue lines were drawn from top to down at the upper 95% limits of agreement, the mean difference (bias), and the lower 95% limits of agreement. Dotted horizontal black lines indicate the 95% confidence interval (CI) for the mean and the agreement limits (defined as the mean difference ± 1.96 times the standard deviation of the differences).