Infliximab Activity with Reflex to Antibody
Ordering Recommendation

Evaluate response failure to infliximab 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 treatment. 
Serum Separator Tube (SST). 
Specimen Preparation
Separate from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.3 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
Available SeparatelyComponentsReference Interval
2013612Infliximab Activity w/Rflx to AntibodyNot Detected
NoIFX Rflx to Neutralizing Antibody ConfirmationNot Detected

Interpretive Data
This test measures the capacity of infliximab to neutralize TNF-alpha activity. Additionally, infliximab neutralizing antibodies (NAb) are titered (reporting the highest dilution of patient sera in which NAb activity is detected).

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 Antibody Titer is...THEN...
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-alpha drug may be appropriate.
0.65 µg/mL or greaterN/AA change to another type of therapy (not targeting TNF-alpha) may be appropriate, if the patient did not respond adequately to infliximab therapy.

Compliance Statement B: 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 Eurodiagnostica. If Infliximab drug level is not detected, then Infliximab Neutralizing Antibody Titer will be added. Additional charges apply.
CPT Code(s)
Component Test Code*Component Chart NameLOINC
2013613Infliximab Activity w/Rflx to Ab
2013614EER Infliximab Activity w/Rflx to Ab
* 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 click the sidebar link to access the Interface Map.
  • Anti-TNF-alpha Drug
  • Human Anti-Chimeric Antibody
  • IFD
  • Infliximab/HACA measurement
  • Remicade
  • TNFa antibody