Infliximab or Biosimilar Activity with Reflex to Antibody

This test measures the capacity of infliximab to neutralize TNF activity. If infliximab is not detected, testing for neutralizing antibodies (NAb) will be performed. Infliximab NAb titer is obtained by identifying the minimal serum dilution at which blocking of infliximab activity is no longer observed.

This test is used to evaluate secondary response failures to infliximab therapy. Secondary response failure is defined as loss of clinical response after initial improvement of clinical signs and symptoms. Therapeutic decision should rest on both the clinical response and the knowledge of the fate of the drug including the emergence of immunogenicity in individual patients.

Circulating infliximab levels have been shown to vary considerably between patients. These differences relate to route and frequency of administration and patient-related features such as age, gender, weight, drug metabolism, and concomitant medications such as methotrexate and other immunosuppressants.


*AGA recommended target trough concentration for reactive monitoring of patients with active IBD on maintenance therapy is 5 ug/mL or greater for infliximab (Feuerstein JD, et al. Gastroenterology. 2017;153:827-834). The AGA makes no recommendation regarding the use of routine, proactive therapeutic drug monitoring in adults with quiescent IBD treated with anti-TNF agents.

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA-certified laboratory and is intended for clinical purposes.