Infliximab (Remicade, Remsima, Inflectra)

The measurement of Infliximab is a useful tool in managing patients who fail to respond (primary failure) or who go on to lose response (secondary failure) to treatment. Monitoring drug levels allows for a personalised approach to drug optimisation by appropriate dose escalation/de-escalation or drug switching/withdrawal.

Measured alone or as part of a profile including anti-Infliximab antibodies.
Assay also measures biosimilars Remsima and Inflectra.

This test is not currently included in the laboratory's UKAS scope of accreditation to ISO15189:2012.
Clinical details: 
Infliximab is a chimeric (mouse-human) monoclonal antibody which specifically targets tumour necrosis factor alpha (TNFα). Infliximab is licensed for use in Gastroenterology (Crohn's diseases, ulcerative colitis), Rheumatology (rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis) and Dermatology (sever plaque psoriasis). Due to its high cost, Infliximab is only indicated in patients with severe disease which is refractory to conventional therapeutic approaches.
Reference range: 

Please use drug levels as a guide. Infliximab Interpretation:

  • Therapeutic drug levels: ≥2.5 µg/mL
  • Intermediate drug levels: 1.2 – 2.4 µg/mL
  • Subtherapeutic drug levels: < 1.2 µg/mL

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

Sample type and Volume required: 
Serum (SST tube or plain) sample is preferred. Plasma (Lithium heparin, citrate or EDTA) is also acceptable. Minimum 300μL serum or plasma required for both drug and anti-drug antibody analysis.
Turnaround time: 
2 weeks
Special sample instructions: 

Collect blood into a serum separation (SST™) or plain tube, preferably shortly before drug administration (trough levels). Centrifuge sample at 3000 rpm for 10 minutes, aliquot serum or plasma and keep in fridge until transport. If transport is going to be delayed by > 5 days, freeze at -20°C and send by first class post at a later date.

Storage and transport: 
Post the sample to Synnovis Central Specimen Reception by first class post (see request form for full address).
Reference Chemistry Laboratory at St Thomas'
020 7188 1264
4th floor, North Wing
St Thomas' Hospital
Westminster Bridge Road
London SE1 7EH
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 19/02/2024