Background An increasing number of studies indicate that the success of treatment with anti-TNF therapy in RA patients depends on circulating levels of these drugs. For (cost-) effective and safe treatment, assays to reliably measure drug levels in patients therefore seem indispensable.
Objectives To test the performance of the newly developed, ready to use CE-IVD SMART ELISA kits from Sanquin for measuring circulating levels of adalimumab and infliximab. And to verify its role as tool for optimising the treatment of RA patients with these drugs.
Methods The ready to use, complete SMART ELISA kits for infliximab (Remicade®) and adalimumab (Humira®) were developed to measure levels in serum, Li-heparin and EDTA plasma. The drugs bind to recombinant TNF coated on the plate through anti-TNF antibodies. Subsequently, the drugs are detected with drug specific HRP-conjugated monoclonal antibodies. Controls are developed for the clinical low and normal concentration range. The performance of the new kits was tested and we did a method comparison with the in-house test of Sanquin Diagnostic Services, the current golden standard.
Results The kit covers the clinically relevant drug concentration range. For samples with concentrations within the clinically relevant area, all recommended dilutions (1:200, 1:1500, 1:2000) give similar results (%CV<10%). In addition, both intra-assay and inter-assay reliability are good (%CV<10%) as well as the precision of the SMART ELISA kits, including for the low (drug ±1 μg/mL) and high control (drug ±5 μg/mL) (%CV<10%). The new CE-IVD kits highly correlated with the well-established tests of Sanquin Diagnostic Services (slope Passing and Bablok 0.9 – 1.1, correlation ≤0.95). Concordance tables for drug concentrations in the low, adequate and high drug concentration range show that more than 95% of the samples were categorized identical.
Conclusions This study shows that ready to use CE-IVD SMART ELISA kits from Sanquin for adalimumab and infliximab levels are highly reliable, with results that are identical to the results from Sanquin Diagnostic Services. This makes the tests an excellent tool for diagnostic laboratories to monitor drug levels in RA patients in order to achieve (cost-) effective, safe and personalised treatment.
Disclosure of Interest None declared