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HelpTest Code LAB2788 Infliximab Quantitation with Reflex to Antibodies to Infliximab, Serum
Additional Codes
INFLIXIMAB AND ANTIBODY, INFXR
Useful For
Trough level quantitation for evaluation of patients undergoing therapy with infliximab, with signs and symptoms of loss of response to therapy.
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INFX | Infliximab, S | No | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INXAB | Infliximab Ab, S | No | No |
Testing Algorithm
Infliximab will be performed by liquid chromatography-tandem mass spectrometry on all specimens. When infliximab results are below 5.1 mcg/mL, testing for antibodies to infliximab will be performed at an additional charge.
For more information see Ulcerative Colitis and Crohn Disease Therapeutic Drug Monitoring Algorithm
Specimen Type
Serum RedSpecimen Required
Patient Preparation:
1. Draw blood immediately before next scheduled dose (trough specimen).
2. 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 mL
Collection Instructions: Centrifuge and aliquot serum into plastic vial within 2 hours of collection.
On-campus collections: Tube to 99 or deliver to University Extension Hospital Room EH318.
Off-campus collections: Centrifuge and aliquot within 2 hours. Specimen to be stored/transported Frozen.
Specimen 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 |
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 correlated with loss of response to infliximab. For infliximab trough concentrations 5.0 mcg/mL or less, testing for antibodies to infliximab (ATI) is suggested.
For infliximab trough concentrations above 5.0 mcg/mL measured in the setting of loss of response to therapy, patients may benefit from treatment with a different pharmaceutical agent.
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/or presence of 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.
Method Description
Infliximab Quantitation:
This test is performed using liquid-chromatography and tandem mass spectrometry. Preanalytical sample preparation includes a trypsin digestion; unique clonotypic peptides from the light chain of the infliximab chimeric structure (IgG1 kappa) are monitored.(Willrich MAV, Murray DL, Barnidge DR, Ladwig PM, Snyder MR. Quantitation of infliximab using clonotypic peptides and selective reaction monitoring by LC-MS/MS. Int Immunopharmacol. 2015;28(1):513-520. doi:10.1016/j.intimp.2015.07.007)
Infliximab Antibodies:
This lab developed immunoassay is designed to measure antibodies-to-infliximab (ATI) in human serum by means of electrochemiluminescence (ECL) on the MesoScale Discovery (MSD) platform. The assay uses a "bridging" format in which the ATI forms a link between biotin labeled infliximab and SULFO-Tag labeled infliximab. The biotin binds to a streptavidin (SA) coated surface and the SULFO-Tag creates a signal in the presence of a conjugate following application of an electric current via the MSD QuickPlex SA120. During sample preparation, serum is mixed with acetic acid to break the infliximab/ATI complex. Biotinylated and SULFO-Tagged infliximab are then added together with buffer containing Tris-HCL pH 10 to neutralize the pH and bind with ATI that is present in the sample. After the incubation with the labeled drug, the calibrators, controls, and samples are added to a SA plate that has been blocked with a solution of bovine serum albumin. The biotinylated infliximab then binds to the SA plate. After an incubation period, the SA plate is washed, and MSD read buffer is added. Immediately after the addition of read buffer, the plate is analyzed on the MSD QuickPlex SQ120. The read buffer provides an appropriate chemical environment for ECL when a voltage is applied to the electrodes on the plate by the MSD QuickPlex SQ120. This voltage causes bound SULFO-Tagged infliximab to emit measurable light. The MSD QuickPlex SQ120 measures the intensity of emitted light and correlates it to a set of standards with known concentrations of ATI by means of a 4-point logistics curve fitting method.(Willrich MAV, Lazar-Molnar E, Snyder MR, Delgado JC. Comparison of clinical laboratory assays for measuring serum infliximab and antibodies to infliximab. J Appl Lab Med. 2018;2(6):893-903. doi:10.1373/jalm.2017.024869)
Report Available
3 to 6 daysSpecimen Retention Time
2 weeksPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
80230
82397-(if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| INFXR | Infliximab QN with Reflex to Ab, S | 39803-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 63000 | Infliximab, S | 39803-2 |
| 36847 | Interpretation | 59462-2 |
Method Name
INFXR, INFX: Selective Reaction Monitoring Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
INXAB: Electrochemiluminescent Bridging Immunoassay with Acid Dissociation
Forms
If not ordering electronically, complete, print, and send 1 of the following with specimen:
-Gastroenterology and Hepatology Test Request (T728)
-Therapeutics Test Request (T831)
-General Request (T239)
Day(s) Performed
Monday through Friday