Infliximab trough levels: A comparison between the Quantum Blue Infliximab assay and the established ELISA

Evaluating the Accuracy and Clinical Utility of AFIAS-10 Point of Care Versus Enzyme-Linked Immunosorbent Assay in Therapeutic Drug Monitoring of Infliximab and Adalimumab

BACKGROUND

New point-of-care (POC) techniques offer rapid results and address some of the limitations of traditional enzyme-linked immunosorbent assay (ELISA) methods, such as lengthy processing times and delays in therapeutic decision making. It is crucial to evaluate the comparability of POC assays with established ELISA methods to ensure accuracy and reliability in therapeutic drug monitoring. This study aimed to evaluate the analytical performance and clinical utility of the AFIAS-10 POC assay compared with the Promonitor ELISA for quantifying serum concentrations of infliximab (IFX) and adalimumab (ADA) and detecting antidrug antibodies (ATIs and ATAs).

METHODS

A prospective study was conducted from October 2023 to April 2024, including 225 samples from patients with immune-mediated diseases. The samples were analyzed using both AFIAS-10 POC and Promonitor ELISA assays. To assess the agreement between the 2 methods in terms of quantification, Bland-Altman analysis was performed by examining the mean difference and establishing limits of agreement.

RESULTS

The Pearson correlation coefficient indicated strong correlations for IFX (r = 0.932) and ADA (r = 0.967) between the 2 assays. The mean difference between POC and ELISA for IFX was -0.78 mcg/mL and for ADA was 1.54 mcg/mL, respectively. The POC assay tended to underestimate IFX concentrations and overestimate ADA concentrations compared with ELISA.

CONCLUSIONS

The AFIAS-10 POC assay demonstrated good correlation and concordance with the ELISA method for the quantification of IFX and ADA, as well as for detecting anti-IFX and anti-ADA antibodies. However, this correlation was notably lower at higher drug concentrations.

Infliximab monitoring in Crohn's disease: a neural network approach for evaluating disease activity and immunogenicity

Background

The treatment for Crohn's disease (CD) has increasingly required the use of biological agents. Safe and affordable tests have led to the active implementation of therapeutic drug monitoring (TDM) in clinical practice, which, although not yet widely available across all health services, has been proven effective.

Objective

To analyze serum infliximab (IFX) and antidrug antibody (ADA) levels in CD patients, compare two tests, as well as construct a prediction of neural network using a combination of clinical, epidemiological, and laboratory variables.

Design

Cross-sectional observational study.

Method

A cross-sectional observational study was conducted on 75 CD patients in the maintenance phase of IFX treatment. The participants were allocated into two groups: CD in activity (CDA) and in remission (CDR). Disease activity was defined by endoscopic or radiological criteria. Serum IFX levels were measured by enzyme-linked immunosorbent assay (ELISA) and rapid lateral flow assay; ADA levels were measured by ELISA. A nonparametric test was used for statistical analysis; p value of ⩽0.05 was considered significant. Differences between ELISA and rapid lateral flow results within the measurement range were assessed by the Wilcoxon test, Passing-Bablok regression, and Bland-Altman method. Prediction models were created using four neural network sets. Neural networks and performance receiver operating characteristic curves were created using the Keras package in Python software.

Results

Most participants exhibited supratherapeutic IFX levels (>7 mg/mL). Both tests showed no difference in IFX levels between the CDA and CDR groups (p > 0.05). The use of immunosuppressive therapy did not affect IFX levels (p > 0.05). Only 14.66% of patients had ADA levels >5 AU/mL, and all ADA-positive participants exhibited subtherapeutic IFX levels in both tests. The median results of both tests showed significant differences and moderate agreement (r = -0.6758, p < 0.001). Of the four neural networks developed, two showed excellent performance, with area under the curve (AUCs) of 82-92% and 100%.

Conclusion

Most participants exhibited supratherapeutic IFX levels, with no significant serum level difference between the groups. There was moderate agreement between tests. Two neural network sets showed disease activity and the presence of ADA, noninvasively determined in patients using IFX by presenting an AUC of >80%.

Observational Study to Compare Biological Drug Concentration Quantification Techniques and Immunogenicity in Patients with Immune-Mediated Diseases

Measuring biological drugs' trough concentrations and the concentrations of anti-drug antibodies is a valuable practice for treatment optimization. ELISA techniques are the gold standard for biological drug concentration quantification, but new techniques such as chemiluminescence immunoassays present some advantages. The aim of this unicentric prospective observational study is to compare the infliximab, adalimumab, vedolizumab and ustekinumab trough levels and anti-adalimumab and anti-infliximab antibodies concentrations obtained when using a chemiluminescent instrument (i-TRACK®, Theradiag, Croissy-Beaubourg, France) and an ELISA instrument (TRITURUS®, Griffols, Barcelona, Spain). Linear regression, Pearson or Spearman tests, Bland-Altman plots and the Cohen kappa test were applied for every sample. The correlation was excellent for both assays in the measurement of all drug concentrations. In general, values were lower when measured using i-TRACK than when using TRITURUS, especially when the values were high. Both techniques proved valuable in clinical practice for monitoring adalimumab and infliximab drug concentration. However, the results were modest for ustekinumab and vedolizumab, so caution is recommended and further research is needed. The limited number of anti-drug antibody-positive samples precluded a comparison between the techniques.

Enhancing Therapeutic Drug Monitoring in Inflammatory Bowel Disease: A Comparative Analysis of Rapid Point-of-Care Infliximab, Adalimumab and Anti-Drug Antibodies' Determination against ELISA

The introduction of point-of-care (POC) assays into clinical practice in patients with inflammatory disease enables on-demand therapeutic decision making. The aim of this study was to compare the POC test Quantum blue (Bühlmann Laboratories) for infliximab (IFX), adalimumab (ADL), and its anti-drug antibodies with the traditional ELISA assay (Promonitor). A total of 200 serum samples were analyzed. Samples were classified into the following three different groups; sub-therapeutic range (IFX < 3 μg/mL and ADL < 5 μg/mL); therapeutic range (IFX: 3-7 μg/mL and ADL: 5-12 μg/mL) and supra-therapeutic range (IFX levels > 7 μg/mL and ADL levels > 12 μg/mL). Significant higher values were measured using the POC test (p < 0.001) for IFX results but no differences in ADL trough levels were observed (p = 0.3101). Spearman's correlation indicated a good correlation between the two assays (rs = 0.88 for ADL and rs = 0.93 for IFX), and McNemar's test revealed significant differences (p = 0.016) when classifying IFX samples between therapeutic and supra-therapeutic ranges but no significant differences were found among the other ranges for either IFX or ADL. These results show that we should be cautious when using these rapid measurement methods, and new targets should probably be defined for IFX when using this new analytical method.

Point-of-care therapeutic drug monitoring of tumour necrosis factor-α inhibitors using a single step immunoassay

Therapeutic drug monitoring (TDM) of tumor necrosis factor-α (TNFα)-inhibitors adalimumab and infliximab is important to establish optimal drug dose and maximize treatment efficacy. Currently, TDM is primarily performed with ELISA techniques in clinical laboratories, resulting in a long sample-to-result workflow. Point-of-care (POC) detection of these therapeutic antibodies could significantly decrease turnaround times and allow for user-friendly home-testing. Here, we adapted the recently developed bioluminescent dRAPPID (dimeric Ratiometric Plug-and-Play Immunodiagnostics) sensor platform to allow POC TDM of infliximab and adalimumab. We applied the two best performing dRAPPID sensors, with limit-of-detections of 1 pM and 17 pM, to measure the infliximab and adalimumab levels in 49 and 40 patient serum samples, respectively. The analytical performance of dRAPPID was benchmarked with commercial ELISAs and yielded Pearson's correlation coefficients of 0.93 and 0.94 for infliximab and adalimumab, respectively. Furthermore, a dedicated bioluminescence reader was fabricated and used as a readout device for the TDM dRAPPID sensors. Subsequently, infliximab and adalimumab patient serum samples were measured with the TDM dRAPPID sensors and bioluminescence reader, yielding Pearson's correlation coefficients of 0.97 and 0.86 for infliximab and adalimumab, respectively, and small proportional differences with ELISA (slope was 0.97 ± 0.09 and 0.96 ± 0.20, respectively). The adalimumab and infliximab dRAPPID sensors, in combination with the dedicated bioluminescence reader, allow for ease-of-use TDM with a fast turnaround time and show potential for POC TDM outside of clinical laboratories.

Validation Study of Novel Point-of-Care Tests for Infliximab, Adalimumab and C-Reactive Protein in Capillary Blood and Calprotectin in Faeces in an Ambulatory Inflammatory Bowel Disease Care Setting

Background and aims: Point-of-care tests (POCT) allow instant measurement of inflammatory markers and drug concentrations. Here, we studied agreement between a novel POCT device and reference methods of measuring infliximab (IFX) and adalimumab (ADL) serum concentrations and C-reactive protein (CRP) and faecal calprotectin (FCP) concentrations of patients with inflammatory bowel disease (IBD). Methods: In this single-centre validation study, IBD patients were recruited in which IFX, ADL, CRP and/or FCP tests were required. IFX, ADL and CRP POCT were performed on capillary whole blood (CWB), obtained via finger prick. Additionally, IFX POCT was performed on serum samples. FCP POCT was performed on stool samples. Agreement between POCT and reference methods was tested using Passing-Bablok regression, intra-class correlation coefficients (ICC) and Bland-Altman plots. Results: In total, 285 patients participated. Passing-Bablok regression identified differences between the reference method and IFX CWB POCT (intercept = 1.56), IFX serum POCT (intercept = 0.71, slope = 1.10) and ADL CWB POCT (intercept = 1.44). There were also differences in the Passing-Bablok regressions of CRP (intercept = 0.81, slope = 0.78) and FCP (intercept = 51 and slope = 0.46). Bland-Altman plots demonstrated that IFX and ADL concentrations were slightly higher with the POCT and CRP and FCP were slightly lower with POCT. The ICC demonstrated almost perfect agreement with IFX CWB POCT (ICC = 0.85), IFX serum POCT (ICC = 0.96), ADL CWB POCT (ICC = 0.82) and CRP CWB POCT (ICC = 0.91) and moderate agreement with FCP POCT (ICC = 0.55). Conclusions: IFX and ADL results were slightly higher with this novel rapid and user-friendly POCT, whereas CRP and FCP results were slightly lower compared to the reference methods.

Quantification of infliximab and adalimumab in human plasma by a liquid chromatography tandem mass spectrometry kit and comparison with two ELISA methods

Background: This study compared the performance of plasma infliximab and adalimumab quantification using a commercially available kit (mAbXmise kit) and mass spectrometry readout to that of two ELISA methods in patients treated for inflammatory bowel disease. Methods & results: The mAbXmise method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) was linear from 2 to 100 μg/ml. It was validated according to international guidelines. Regarding cross-validation for infliximab (n = 70), the mean bias with LC-MS/MS assay was approximately threefold higher with the commercial ELISA assay compared with the in-house ELISA (-6.1 vs -1.8 μg/ml, respectively). The mean bias between the LC-MS/MS assay and in-house ELISA was -1.2 μg/ml for adalimumab (n = 35). Conclusion: The LC-MS/MS method is a powerful alternative to immunoassays to monitor concentrations of infliximab and adalimumab.