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HelpTest Code INFXP Infliximab Quantitation with Antibodies to Infliximab, Serum
Specimen Required
Patient Preparation: For 12 hours before specimen collection, patient should not take multivitamins or dietary supplements (eg, hair, skin, and nail supplements) containing biotin (vitamin B7).
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1.2 mL Serum
Collection Instructions:
1. Draw blood immediately before next scheduled dose (trough specimen).
2. Within 2 hours of collection, centrifuge and aliquot serum into plastic vial.
Secondary ID
620151Useful For
Evaluating patients for loss of response, partial response on initiation of therapy, autoimmune or hypersensitivity reactions, primary nonresponse, reintroduction after drug holiday, endoscopic/computed tomography enterography recurrence (in inflammatory bowel disease), acute infusion reactions and proactive monitoring
These assays do not differentiate between the originator and biosimilar products.
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INFX | Infliximab, S | Yes, (INFXR) | Yes |
| INXAB | Infliximab Ab, S | No | Yes |
Testing Algorithm
When this test is ordered, infliximab quantitation and testing for antibodies to infliximab will always be performed.
For more information see Ulcerative Colitis and Crohn Disease Therapeutic Drug Monitoring Algorithm.
Method Name
INFX: Selective Reaction Monitoring Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
INXAB: Electrochemiluminescent Bridging Immunoassay with Acid Dissociation
Specimen Type
Serum RedSpecimen Minimum Volume
Serum: 0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days |
| Frozen | 28 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | Reject |
| Heat-Treated | Reject |
Reference Values
INFLIXIMAB QUANTITATION:
Limit of quantitation is 1.0 mcg/mL. Therapeutic ranges are disease specific.
Pediatric reference ranges are not established.
INFLIXIMAB ANTIBODIES
Absence of antibodies to infliximab (ATI) is defined as <50 U/mL
Presence of ATI is reported as positive when concentrations are ≥50 U/mL
Interpretation
Low trough concentrations may be associated with loss of response to infliximab due to possible development of an immune response to infliximab. Testing for antibodies to infliximab is suggested in patients with trough concentrations less than or equal to 5.0 mcg/mL.
Infliximab trough concentrations less than or equal to?5.0 mcg/mL in patients with loss of response to therapy may suggest a possible benefit of treatment with a different monoclonal antibody therapy.
Infliximab concentrations less than or equal to 35 mcg/mL suggest possible testing at a time point other than trough if IV infusions are used and should be evaluated within the clinical context of the patient.
Interpretation and patient management will be different according to disease state, clinical presentation (symptomatic versus appropriate response to therapy), several other laboratory tests and a combination of the drug concentration and presence of anti-drug antibodies to infliximab (ATI).
A low titer ATI is reported with a quantitative value of 50 to 499 U/mL. A high-titer ATI is reported with a quantitative value greater than or equal to 500 U/mL, using the Mayo Clinic assay.
|
Infliximab quantitation, mcg/mL |
Antibodies to infliximab |
Comment |
|
<5 |
Negative |
Absence of detectable antibody-to-infliximab (ATI). Low concentration of infliximab (IFX) may be attributable to other parameters related to infliximab clearance. |
|
<5 |
Positive |
Presence of ATI detected, which correlates with low concentration of infliximab. ATIs may be associated with increased clearance and lower circulating concentrations of IFX. |
|
5-10 |
Negative |
Absence of detectable ATI.
At this concentration of IFX, a low-titer ATI (50-499 U/mL) cannot be completely excluded. However, the presence of a high-titer ATI (≥500 U/mL) is unlikely.
If there is clinical suspicion for a low-titer ATI, suggest submission of a new sample obtained at trough.
This test has demonstrated drug tolerance of up to 100 mcg/mL IFX for ATI ≥500 U/mL and up to 10 mcg/mL IFX for ATI <500 U/mL |
|
|
Low positive (50-499 U/mL) |
Presence of ATI detected. At this concentration of IFX, the detected titer of the ATI may be modestly underestimated.
This test has demonstrated drug tolerance of up to 100 mcg/mL IFX for ATI ≥500 U/mL and up to 10 mcg/mL IFX for ATI <500 U/mL |
|
|
High positive (≥500 U/mL) |
Presence of ATI detected.
This test has demonstrated drug tolerance of up to 100 mcg/mL IFX for ATI ≥500 U/mL and up to 10 mcg/mL IFX for ATI <500 U/mL |
|
>10 |
Negative |
Absence of detectable ATI.
At this concentration of IFX, a low-titer ATI (50-499 U/mL) cannot be completely excluded. The presence of a high-titer ATI (≥500 U/mL) is unlikely, but also cannot be completely excluded.
If there is clinical suspicion for an ATI, suggest submission of a new sample at trough, preferably during maintenance phase. This test has demonstrated drug tolerance of up to 100 mcg/mL IFX for ATI ≥500 U/mL and up to 10 mcg/mL IFX for ATI <500 U/mL |
|
|
Low positive (50-499 U/mL) |
Presence of ATI detected. At this concentration of IFX, the detected titer of the ATI may be underestimated.
Suggest submission of a new sample obtained at trough, preferably during maintenance phase.
This test has demonstrated drug tolerance of up to 100 mcg/mL IFX for ATI ≥500 U/mL and up to 10 mcg/mL IFX for ATI <500 U/mL |
|
|
High positive (≥500 U/mL) |
Presence of ATI detected. This test has demonstrated drug tolerance of up to 100 mcg/mL IFX for ATI ≥500 U/mL and up to 10 mcg/mL IFX for ATI <500 U/mL |
Method Description
Infliximab Quantitation:
Testing for infliximab is performed using a laboratory-developed test using liquid chromatography tandem mass spectrometry.(Unpublished Mayo method)
Infliximab Antibodies:
Testing for antibodies to infliximab is performed using a laboratory-developed immunoassay.(Unpublished Mayo method)
Day(s) Performed
INFX: Monday through Friday
INXAB: Monday, Wednesday, Friday
Report Available
3 to 6 daysSpecimen Retention Time
2 weeksPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
INFX-80230
INXA -82397
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| INFXP | Infliximab QN with Antibodies, S | 103791-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 63417 | Infliximab Ab, S | 72623-2 |
| 63000 | Infliximab, S | 39803-2 |
| 36847 | Interpretation | 59462-2 |
| 36654 | INXAB Interpretation | 59462-2 |
Forms
If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Test Request (T728) with the specimen.