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HelpTest Code INFXP Infliximab Quantitation with Antibodies to Infliximab, Serum
Specimen Required
Patient Preparation:
1. Draw blood immediately before next scheduled dose (trough specimen).
For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1.2 mL
Collection Instructions: Centrifuge and aliquot serum into plastic vial within 2 hours of collection.
Useful For
Trough level quantitation for evaluation of patients undergoing therapy with infliximab for proactive or reactive therapeutic drug monitoring.
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
Reporting Name
Infliximab QN with Antibodies, SSpecimen Type
Serum RedSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| 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
Results above 35 mcg/mL are suggestive of a blood draw at a time-point in treatment other than trough.
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 antibodies to infliximab.
|
IFX quant, mcg/mL |
ATI, U/mL |
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 |
Day(s) Performed
INFX: Monday, Wednesday, Thursday
INXAB: Monday, Wednesday, Friday
Report Available
3 to 6 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
INFX - 80230
INXAB - 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.