Background and Importance ELISA is the most commonly used technique to determine adalimumab (ADL) levels in patients with inflammatory bowel disease (IBD), as it is simple and inexpensive. Its disadvantage is that it requires a specialised laboratory and several tens of samples have to be accumulated to make the cost of each determination more efficient, with the consequent delay in obtaining the results. Rapid tests make it possible to obtain levels in a very short time (15 minutes) and to act immediately to optimise biological therapy.
Aim and Objectives The aim of this study is to compare the reference technique for quantifying ADL levels using ELISA with quantification using a rapid test, the point of care (POC) test.
Material and Methods ADL levels of 56 IBD patients were tested by both methods. Samples were obtained prior to ADL infusion. Promonitor®ADLv2 kits from Progenika Biopharma were used for the enzyme-linked immunoassay (ELISA). For the rapid assay (POC), the Quantum Blue® Adalimumab Lateral Flow Immunochromatography technique (BÜHLMANN Laboratories) was used.
Quantitative comparison of both techniques was assessed with Bland-Altman plots, Student’s t-test and regression line to test for agreement between the two techniques. A p-value of <0.05 was considered statistically significant. The 95% limits of agreement were calculated using the mean ± 1.96*SD. Correlation was assessed using Pearson’s correlation coefficient (r). Statistical analyses were performed with the R®v4.1.2 package.
Results The median ADL concentration was 12.4 μg/mL (range 0.3–24.4 μg/mL) using the ELISA test and 13.8 μg/mL (range 1–35 μg/mL) using the POC test (Quantum Blue®). The Pearson correlation for both was high (r=0.87, p<0.001) and the regression line y=1.06x+1.90, whose slope of 1.06 indicates good agreement between the two techniques. The mean difference between ELISA and POC test was -2.76 μg/mL (95%CI, -11.70–6.18) (<0.05). The Bland-Altman plot indicates that at concentrations above approximately 15 μg/mL, the rapid test (POC) overestimates the ADL concentration values compared to the ELISA technique.
Conclusion and Relevance The Quantum Blue® Adalimumab POC rapid test shows high correlation and concordance and minimal acceptable differences compared to the reference ELISA tests, making it reliable and allowing results to be obtained within minutes.
Conflict of Interest No conflict of interest.
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