Infliximab or Biosimilar Activity with Reflex to Antibody
Use to evaluate response failure to infliximab or biosimilar therapy. Use to determine and adjust dosage or identify the need for change to another anti-TNF-α inhibitor.
If infliximab drug level is not detected, infliximab neutralizing antibody will be added. To assess for both infliximab activity and neutralizing antibody titer regardless of infliximab drug level, see Infliximab or Biosimilar Activity and Neutralizing Antibody (2008320).
New York DOH Approval Status
Collect specimens before next infliximab or biosimilar treatment.
Serum Separator Tube (SST).
Separate from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.5 mL)
Contaminated, hemolyzed, icteric, or lipemic specimens.
After separation from cells: Ambient: 48 hours; Refrigerated: 4 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles)
Cell Culture/Quantitative Chemiluminescent Immunoassay (CLIA)
|Infliximab Activity w/Rflx to Ab||Not Detected|
|Infliximab Neutralizing Antibody Titer||Not Detected|
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.
|Clinical Interpretation of Infliximab and Antibody Testing Results in the Context of Treatment Failure|
||Infliximab Neutralizing Antibody Titer
|Not Detected||Not Detected||Sub-therapeutic dose. A higher dosage of infliximab or shortening the dosing interval may be appropriate.|
|Not Detected||Detected||Likely immune-mediated treatment failure. A change to another anti-TNF drug may be appropriate.|
|Detected - Below Target*||N/A||Sub-therapeutic dose. A higher dosage of infliximab or shortening the dosing interval may be appropriate.|
|Detected - Above Target*||N/A||A change to another type of therapy (not targeting TNF) may be appropriate, if the patient is not responding adequately to infliximab therapy.|
Laboratory Developed Test (LDT)
This test is performed pursuant to an agreement with Svar Life Sciences. If Infliximab drug level is not detected, then Infliximab Neutralizing Antibody Titer will be added. Additional charges apply.
80230; if reflexed, add 82397
|Component Test Code*||Component Chart Name||LOINC|
|2013613||Infliximab Activity w/Rflx to Ab||39803-2|
|2013614||EER Infliximab Activity w/Rflx to Ab||11502-2|
- Anti-TNF-alpha Drug
- Human Anti-Chimeric Antibody
- Infliximab/HACA measurement
- TNFa antibody