Infliximab and anti-infliximab antibody

 
Referred to Reference Chemistry Laboratory, St Thomas' Hospital, London SE1 7EH
 

Alternative names, keywords

Anti-TNF alpha drugs, Anti-Infliximab antibody, Remsima, Flixabi, Inflectra.

Samples required

● Clotted blood (gold cap, 5 mL tube). Smaller tubes are available for paediatric samples.

Trough level recommended (immediately before the next dose is due).

For prompt referral of sample please specify which drug patient is on.

Test indications

Monitoring infliximab treatment: primary treatment failure (non-response), secondary loss of response, prediction of infusion reactions, adherence to therapy, reintroduction after drug interruption.

Interpretation requires full clinical details: drug dosage/ frequency, previous exposure to other biologics, time of sampling, duration of therapy and clinical assessment.

Reference range

Interpretation guide:
  Therapeutic drug levels:      ≥ 2.5 µg/mL
  Intermediate drug levels:   1.2 - 2.4 µg/mL
  Sub-therapeutic drug levels:  <1.2 µg/mL

Anti-infliximab antibody will be performed if infliximab is < 2.5 µg/mL

Please note change in methodology from ELISA to CLIA from 2 June 2025. Please use results from the new protocol as a baseline for future optimisation of therapy.

Infliximab target concentrations:

Induction/post-induction:

Week 2 therapeutic target: 20 - 25 ug/mL
Week 6 therapeutic target: 15 - 20 ug/mL
Week 14 therapeutic target: 7 - 10 ug/mL

Maintenance therapeutic target: at least 5 - 10 ug/mL

Target concentrations are based on Cheifetz* et al. (2021) and apply only to intravenous infliximab in inflammatory bowel disease. Therapeutic levels for subcutaneous infliximab have not been established. All TDM thresholds are estimates based on population data. Results should always be interpreted in the context of the clinical situation.

*Cheifetz et al, Am J Gastroenterol 2021;116:2014-2025.

 

Anti-infliximab antibody: 0 - 10 ng/mL

In the presence of infliximab, anti-infliximab antibody may not be detected. 

Turnaround time

Referral lab quotes turnaround time of 2 weeks, however additional time must be allowed for packing, dispatch and delivery of sample, and return and processing of results.

Enquiries

Biochemistry (Referrals)
 
Details