The drug Etanercept (trade name Enbrel?) is a dimeric fusion protein consisting of the extracellular ligand-binding portion of the human 75 kilodalton (p75) tumor necrosis factor receptor (TNFR) linked to the Fc portion of human IgG1. Etanercept binds specifically to human tumor necrosis factor alpha (TNF-?) and blocks its interaction with cell surface TNF receptors. It was possible to show that the surveillance of circulating Etanercept concentration during maintenence therapy represents a direct and/or indirect factor for immunogenicity and some other side effects. In this context, identification of biomarkers for (non-)response and risk factors for adverse drug reactions that might be related to serum concentrations and maintaining the effective concentration of Etanercept in order to potentially avoid some side effects with a reliable method might be beneficial. Sample Types: serum, plasma. Range: 6 - 200 ng/mL. Sensitivity: 5 ng/mL. Time: 2 hours ? The Eagle Biosciences Etanercept ELISA Assay Kit is an enzyme immunoassay for the precise analytical determination of free Etanercept in serum and plasma. The Etanercept ELISA Assay Kit is for research use only and not to be used in diagnostic procedures.