Comparative evaluation of point of care assay with ELISA techniques for quantifying serum concentrations of ustekinumab in inflammatory bowel disease patients.

Objectives: To evaluate the analytical performance and clinical utility of the POC-AFIAS assay in comparison with two ELISA established assays for quantifying serum concentrations of ustekinumab.

Methods: A prospective study was conducted. Consecutive serum samples from adult patients undergoing treatment with ustekinumab were collected. Three analytical techniques were compared for the quantification of ustekinumab serum concentrations: the AFIAS-10® POC assay (POC-AFIAS), the Promonitor® ELISA assay (ELISA-PRO), and the ELISA Ridascreen® assay (ELISA-RDSC). Ustekinumab concentrations were evaluated within three therapeutic ranges: <1μg/mL, 1-4.5μg/mL, and >4.5μg/mL. Statistical analysis included Pearson correlation, intra-class correlation coefficient, and Bland-Altman analysis.

Results: A total of 104 patients were included in the study. The median ustekinumab concentrations measured were 5.22μg/mL (POC-AFIAS), 3.99μg/mL (ELISA-PRO), and 4.50μg/mL (ELISA-RDSC). Strong correlations were observed between techniques (POC-AFIAS and ELISA-PRO: r=0.921, POC-AFIAS and ELISA-RDSC: r=0.940, ELISA-PRO and ELISA-RDSC: r=0.976). The Bland-Altman analysis revealed a bias difference of 1.81μg/mL between POC-AFIAS and ELISA-PRO, and 1.27μg/mL between POC-AFIAS and ELISA-RDSC. Agreement rates varied by therapeutic range, with the highest agreement observed within the therapeutic range (97.3%) and lower agreement for supra-therapeutic concentrations (74.6%).

Conclusion: This study demonstrated that the POC-AFIAS assay provides comparable results to established ELISA techniques for quantifying serum concentrations of ustekinumab, particularly within the therapeutic range. The findings suggest that the POC-AFIAS assay offers a rapid and effective tool for managing ustekinumab therapy in clinical practice.