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P202 Quantum blue anti-infliximab: development and evaluation of a point of care rapid test for measuring anti-infliximab antibodies in human serum

F. Bantleon1, M. Schneider*1, B. Ricken1, S. Velayutham1, D. Trapani1, J. Afonso2, F. Magro2, A. Abel1

1BÜHLMANN Laboratories AG, Schoenenbuch, Switzerland, 2Faculty of Medicine, University of Porto, Department of Biomedicine, Unit of Pharmacology and Therapeutics, Porto, Portugal

Background

The treatment of patients suffering from an inflammatory disease, like inflammatory bowel disease (IBD) may involve biologicals like infliximab. However, infliximab is a chimeric human/murine monoclonal antibody and can induce a significant immune response. Within this immune response different anti-infliximab antibodies are formed, belonging to different isotypes (eg, IgM, IgG1, IgG4, and IgE) with different specificities and affinities. The detection of these anti-infliximab antibodies is crucial to adjust the therapy with infliximab or to justify a switch of the used drug. For the fast and easy detection of the anti-infliximab response a lateral flow test was developed and preliminary evaluated.

Methods

A drug-sensitive bridging lateral flow test was developed using infliximab-fragment coated gold nanoparticles and membrane immobilised infliximab to detect polyclonal anti-infliximab antibodies in a diluted human serum sample. Standardisation is based on a specific monoclonal anti-infliximab antibody. Using this approach limit of detection (LoD) and limit of quantification (LoQ) were determined according to CLSI EP17-A2 guideline. The influence of rheumatoid factors as well as various blood conditions was evaluated. Patient samples were used to compare the Quantum Blue® Anti-Infliximab rapid test with a commercially available ELISA test. These results were used to establish a ROC curve analysis and to identify a clinical relevant cut-off value.

Results

The current Quantum Blue® Anti-Infliximab test allows the analysis of diluted human serum samples within 15 min. The samples are diluted in chase buffer (1:10) before application on the test cassette. The readout is performed with a Quantum Blue® Reader resulting in a measuring range of 0.5 to 12 μg/ml. Due to missing international standard material and the polyclonal immune response in patients, the Quantum Blue® Anti-Infliximab was classified as semi-quantitative. The test exhibits a LoD of 0.31 μg/ml and a LoQ of 0.5 μg/ml. Rheumatoid factors as well as various blood conditions showed no interference to test results. A clinical cut-off value of 1.44 μg/ml results in a sensitivity of 0.86 and a specificity of 0.94 obtained by ROC curve analysis with 78 patient samples.

Conclusion

The here presented Quantum Blue® Anti-Infliximab test allows the fast and easy detection of anti-infliximab antibodies in human serum within 15 min. The assay can be carried out with a minimum of external equipment and may therefore support a fast adaption of the treatment regime, providing a valuable tool for pro-active therapeutic drug monitoring.