Infliximab Level and Anti‑Drug Antibody for Rheumatic Diseases
Also known as: IFX, infliximab-dyyb, TNF-alpha inhibitor, ATI, Human Anti-Chimeric Antibody
Use
This test measures serum infliximab concentrations and anti‑drug (anti‑infliximab) antibodies in individuals with rheumatic diseases who have experienced failure of treatment with infliximab or its biosimilar, facilitating differentiation between pharmacokinetic failure (low drug levels, absent antibodies) and immunogenicity (presence of anti‑drug antibodies), and thereby informing dose adjustment or therapeutic switching decisions. ([questdiagnostics.com](https://www.questdiagnostics.com/healthcare-professionals/about-our-tests/autoimmune-diseases/assessing-therapeutics?utm_source=openai))
Special Instructions
Assays are valid for the infliximab originator and are immunoassay‑based. Quest infliximab assays are validated for the biosimilar Inflectra® (infliximab‑dyyb). Use the same assay consistently for monitoring longitudinally. ([questdiagnostics.com](https://www.questdiagnostics.com/healthcare-professionals/clinical-education-center/faq/faq201?utm_source=openai))
Limitations
Concentrations may vary between assay methods; therefore, the same assay method should be used for monitoring a given patient. Immunoassay may not distinguish originator from biosimilars beyond Inflectra validation. ([questdiagnostics.com](https://www.questdiagnostics.com/healthcare-professionals/clinical-education-center/faq/faq201?utm_source=openai))
Methodology
Immunoassay (Multiplex Protein Panel)
Biomarkers
Result Turnaround Time
Not provided.
Related Documents
For more information, please review the documents below
Not provided.