Background: Adalimumab is a human monoclonal antibody directed against tumor necrosis factor alpha (TNFα) used for the treatment of inflammatory diseases like Crohn's Disease (CD) and Ulcerative Colitis (UC). For efficient treatment trough levels of adalimumab need to be adjusted within a therapeutic window, which is 5 to 10 μg/mL (Moos et al., 2015). A rapid test allows a much faster reporting of trough levels, providing a great advantage over test formats that need samples to be send in to a central lab. Here we report current results of the completed Quantum Blue® Adalimumab test optimization. The test is now under validation.
Methods: The sandwich lateral flow immunoassay uses a TNFα coated gold label and a highly specific monoclonal antibody to detect adalimumab in a diluted human serum sample. Sensitivity of the assay was estimated via Limit of Detection (LoD) and Limit of quantification (LoQ) according to CLSI EP17-A2. Moreover the assay was evaluated regarding cross-reactivity with other therapeutic antibodies targeting TNFα, influence of rheumatoid factors (RF) and high dose hook effect. A method comparison was performed using a commercial available ELISA (RIDASCREEN® ADM Monitoring, Art. No. G09043, R-Biopharm, Darmstadt, Germany) to compare the trough level results of 40 adalimumab treated patients.
Results: The current Quantum Blue® Adalimumab test allows analysis of serum samples within 15 minutes. The samples are diluted 1:20 in chase buffer before application on a test cassette (volume 80 μL). The readout is performed with the Quantum Blue® Reader resulting in concentration levels of adalimumab in μg/mL.
The test exhibits a LoD of 0.2 μg/mL and a LoQ of 0.69 μg/mL. These data ensure a measuring range of 1 to 35 μg/mL of adalimumab patient samples. No high dose hook effect was detected for samples containing up to 1000 μg/mL adalimumab. Other therapeutic TNFα blockers, like infliximab and golimumab, showed no cross-reactivity with the Quantum Blue® Adalimumab test, furthermore RFs showed no influence on correct measurement of adalimumab at the tested concentrations. The method comparison revealed a slope of 1.12 and a regression coefficient (r2) of 0.90 (Passing-Bablok). A Bland-Altman analysis showed a bias of 1.88% confirming the overall excellent correlation of the two methods.
Conclusions: The BÜHLMANN Quantum Blue® Adalimumab assay enables the quantitative determination of adalimumab trough level in serum with time to result of only 15 minutes. The developed assay allows to measure adalimumab over a wide range. Hence, it represents a valuable tool for the clinician to assess the adalimumab trough level.