Infliximab or Biosimilar Activity and Neutralizing Antibody
Ordering Recommendation

Evaluate response failure to infliximab or biosimilar therapy. Determine and adjust dosage or identify the need for change to another anti-TNF-α inhibitor.

Cell Culture/Quantitative Chemiluminescent Immunoassay/ Semi-Quantitative Chemiluminescent Immunoassay
Mon, Wed, Thu, Sat
2-3 days
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
Collect specimens before infliximab or biosimilar treatment. 
Serum separator tube. 
Specimen Preparation
Separate serum from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.5 mL) 
Storage/Transport Temperature
Unacceptable Conditions
Contaminated, hemolyzed, icteric, or lipemic specimens. 
After separation from cells: Ambient: 48 hours; Refrigerated: 4 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles) 
Reference Interval
Reference Interval
NoInfliximab ActivityNot Detected
NoInfliximab Neutralizing Antibody TiterNot Detected

Interpretive Data
This test measures the capacity of infliximab to neutralize TNF-alpha activity. Additionally, infliximab neutralizing antibodies (NAb) are titered (reporting 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.

IF Infliximab
Activity is....
AND Infliximab Neutralizing
Ab. Titer is....
Not DetectedNot DetectedA higher dosage of infliximab or shortening the dosing interval may be appropriate.
Not Detected1:20 or greaterA change to another anti-TNF-α drug may be appropriate.
0.65 ug/mL or greaterNot DetectedA change to another type of therapy (not targeting TNF-α) may be appropriate.
0.65 ug/mL or greater1:20 or greaterRepeat testing is suggested to rule out decreasing infliximab activity and/or increasing infliximab neutralizing antibodies.

Statement B: Compliance Statement B: For laboratory developed tests not using a RUO kit, and for FDA approved, cleared or 510(k) exempt assays with alterations. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.

This test is performed pursuant to an agreement with Euro Diagnostica.
Hotline History
View Hotline History
Component Test Code*Component Chart NameLOINC
2008321Infliximab Activity39803-2
2008322Infliximab Neutralizing Antibody Titer86897-6
2008323EER Infliximab11526-1
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please view this test within the Laboratory Test Directory found at
  • Anti-TNF-alpha Drug
  • Human Anti-Chimeric Antibody
  • IFD
  • Inflectra
  • Infliximab level
  • Infliximab-abda
  • Infliximab-dyyb
  • Infliximab/HACA measurement
  • Remicade
  • Renflexis
  • TNFa antibody