Infliximab (IFX) is a chimeric monoclonal antibody which has proven its efficacy in the treatment of inflammatory diseases. However, its efficacy can be limited by the development of anti-IFX antibodies (ATI) resulting in a therapeutic failure of IFX. ATI plasmatic monitoring is then indicated to optimize IFX treatment. The aim of this study was to validate an ELISA (enzyme linked immuno sorbent assay) method of ATI plasmatic monitoring.
Methods: Assessment of performance was based on the study of correlation and concordance (Bland Altman method) of the absorbances measured by the two readers. ELISA kit validation was made by calculating the accuracy and the exactitude.
Results: We collected 23 samples. Their mean age was 46 years and sex ratio M/W was 0.92. In nine cases, plasmatic AIT were positive and in 14 cases, they were not detected. Correlation between the two readers showed a correlation coefficient r2 of 99.95%. Concordance limits of the confidence interval 95% were [-112.768%-41.425%] with a bias of -35.671%. Repeatability and reproductibility were checked by a positive control and coefficients of variation were respectively of 5.574% and 14.184%. Limits of detection and quantification were respectively of 0.046 and 0.086. The positive predictive value was 0.5 and the negative predictive value was 1. The sensitivity was 100% and the specificity was 83%.
Conclusion: The assessment of the performance of the tested microplate reader and the validation of the tested ELISA kit showed good results allowing ATI routine measurement to optimize therapeutic management of patients treated by IFX.
Keywords: ELISA; anti-infliximab antibodies; assay methods; therapeutic drug monitoring.