Comparison of Three Assays to Quantify Infliximab, Adalimumab, and Etanercept Serum Concentrations.
To optimize treatment of inflammatory diseases, interest in the measurement of anti-tumor necrosis factor alpha (anti-TNFα) serum drug concentrations is increasing. Preferably, assays for the detection of these drugs should be compared using the same reference material. In this study, 2 commercially available enzyme-linked immunosorbent assays (ELISAs) and a commercially available bioassay for the determination of anti-TNFα drugs are compared.



Serum samples from infliximab-, adalimumab-, and etanercept-treated patients, control samples from ustekinumab-treated patients, and healthy donors were obtained. ELISAs manufactured by Sanquin and Theradiag and the iLite reporter gene-based bioassay from Biomonitor were compared.



Sanquin, Theradiag, and iLite assays concordantly (100%) detected infliximab, adalimumab, and etanercept in the relevant patient groups. The Sanquin ELISAs specifically detected the anti-TNFα drug they were designed for, whereas the Theradiag and iLite showed cross-reactivity with other anti-TNFα drugs. Ustekinumab was not detected in any of the assays. Sanquin, Theradiag, and iLite exhibited linear quantitative correlation for all drug concentration assays. However, there were statistically significant quantitative differences in measured concentrations.



All 3 commercially available assays seem suitable for therapeutic drug monitoring of anti-TNFα drugs, allowing sensitive and comparable detection of infliximab, adalimumab, and etanercept concentrations, however with differences in specificity and recovery.
Departments of *Dermatology, †Hospital Pharmacy, and ‡Immunology, University Medical Center, Erasmus MC, Rotterdam, the Netherlands.
Ji S
JS
van Bezooijen
Birgit C P
BC
Koch
Martijn B A
MB
van Doorn
Errol P
EP
Prens
Teun
T
van Gelder
Marco W J
MW
Schreurs
D000068879:Adalimumab / Q000097:blood* / Q000627:therapeutic use; D000893:Anti-Inflammatory Agents / Q000097:blood* / Q000627:therapeutic use; D018501:Antirheumatic Agents / Q000097:blood* / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000188:drug therapy; D003429:Cross Reactions / Q000502:physiology; D016903:Drug Monitoring / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D000068800:Etanercept / Q000097:blood* / Q000378:metabolism / Q000627:therapeutic use; D006801:Humans; D000069285:Infliximab / Q000097:blood* / Q000627:therapeutic use; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000893:Anti-Inflammatory Agents; D018501:Antirheumatic Agents; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D000068879:Adalimumab; D000068800:Etanercept