Trough level quantitation for evaluation of patients undergoing therapy with infliximab, with signs and symptoms of loss of response to therapy.
| Test Id | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INFX | Infliximab, S | No | Yes |
| Test Id | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INXAB | Infliximab Ab, S | No | No |
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
INFXR, INFX: Selective Reaction Monitoring Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
INXAB: Electrochemiluminescent Bridging Immunoassay with Acid Dissociation
Anti-TNF inhibitor
Auto-immune disease treatment
INFXR
INFX
INXAB
REMICADE
RENFLEXIS
Inflectra
Infliximab abda
Infliximab
63437
63000
63417
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
Serum Red
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.
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)
0.5 mL
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | Reject |
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days | |
| Frozen | 28 days |
Trough level quantitation for evaluation of patients undergoing therapy with infliximab, with signs and symptoms of loss of response to therapy.
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
Infliximab is a chimeric immunoglobulin (IgG1 kappa) targeting tumor necrosis factor-alpha (TNF-a) and it is currently US Food and Drug Administration (FDA)-approved for the treatment of multiple inflammatory conditions. Infliximab binds to soluble TNF-a and transmembrane homotrimers, which are found on the surface of macrophages and T cells, with similar affinity. Infliximab has the ability to mediate complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity, which leads to the lysis of target cells.
The reference product for infliximab is Remicade (Janssen Pharmaceuticals) and several biosimilar products are FDA-approved, including but not limited to: Renflexis (infliximab-abda, Organon), Inflectra (infliximab-dyyb, Pfizer Inc), Ixifi (infliximab-qbtx, Pfizer Inc), and Avsola (infliximab-axxq, Amgen). Inflectra, Renflexis, and Avsola have the same primary amino acid sequence as Remicade. Therefore, “infliximab” will be used to refer to both the reference product and the biosimilar products interchangeably. This test cannot distinguish between Remicade and the infliximab biosimilar products.
A biosimilar product is a biological product that it is highly similar to an FDA-approved biological product, known as the reference product, but manufactured by a different company. No clinically meaningful differences in terms of safety and effectiveness from the reference product are present. Only minor differences in clinically inactive components are allowable in biosimilar products. In contrast to generic medications, a prescription of biosimilars needs to come from the ordering physician and not the dispensing pharmacy (pharmacies cannot substitute a biosimilar for another medication; a separate prescription is required).
This assay has been verified to measure antibodies to infliximab (ATI) (Remicade and the biosimilars infliximab-dyyb, infliximab-abda, and infliximab-axxq) with no analytical differences between the detection of ATI for the four drugs. It is expected that antibodies developed against other biosimilars would also demonstrate no significant analytical differences for the drug quantitation.
Infliximab pharmacokinetic properties may vary with disease and clearance is affected by concomitant use of immunosuppressants, high concentrations of TNF-a and C-reactive proteins,(1,2) low albumin concentrations, high body mass index, and presence of ATI, also known as human antichimeric antibodies.(3) Male patients seem to clear infliximab faster than female patients.(3)
Several studies have demonstrated that infliximab quantitation in the setting of loss of response to therapy can aid in patient management, as trough concentrations defined as therapeutic have been associated with superior clinical response and improved prognosis.(4-6) Other studies have shown that proactive monitoring of infliximab concentrations in the maintenance stage, even when there is clinical response was more effective in sustaining disease control than standard therapy without any therapeutic drug monitoring in preventing disease worsening during a 52-week period.(7)
Evaluation of infliximab concentrations may be of value for all inflammatory diseases for which it is prescribed. Primary indications for testing of infliximab include 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.
Measurement of infliximab concentrations is indicated at trough, immediately prior to the next scheduled infusion. Infliximab concentrations tend to reach steady state and stabilize after 14 weeks (approximately 100 days). Quantitation of peak infliximab concentrations is strongly discouraged.
Low trough concentrations may be correlated with loss of response to infliximab. Assessment of ATI is suggested when infliximab quantitation at trough is 5.0 mcg/mL or less.
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 > or =50 U/mL
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.
Toxicity effects other than acute hypersensitivity infusion reactions have not been described nor correlated with infliximab concentrations.
During the initial induction phase of treatment (weeks 0, 2, and 6), steady-state has not been achieved and concentrations of infliximab may vary significantly between infusions.(3)
Therapeutic concentrations of infliximab may vary according to the disease (eg, Crohn disease versus ulcerative colitis versus rheumatoid arthritis).
The American Gastroenterology Association established thresholds associated with positive outcomes for adults with active inflammatory bowel disease based on several clinical studies.(8)
Samples containing more than 12.5 ng/mL biotin (vitamin B7) may interfere (in the form of depressed signal) with INXAB / Infliximab Antibodies, Serum.
For antibodies-to-infliximab (ATI), pediatric and adult reference ranges were validated, and the presence of an ATI is established as greater than or equal to 50 U/mL by our bridging electrochemiluminescent/acid dissociation method.
The presence of endogenous infliximab is a recognized interference in most ATI methods. This assay includes an acid dissociation step, which partially mitigates this interference.
1. Colombel JF, Sandborn WJ, Reinisch W, et al. Infliximab, azathioprine, or combination therapy for Crohn's disease. N Engl J Med. 2010;362(15):1383-1395. doi:10.1056/NEJMoa0904492
2. Jurgens M, Mahachie John JM, Cleynen I, et al. Levels of C-reactive protein are associated with response to infliximab therapy in patients with Crohn's disease. Clin Gastroenterol Hepatol. 2011;9(5):421-427.e1. doi:10.1016/j.cgh.2011.02.008
3. Ordas I, Mould DR, Feagan BG, Sandborn WJ. Anti-TNF monoclonal antibodies in inflammatory bowel disease: pharmacokinetics-based dosing paradigms. Clin Pharmacol Ther. 2012;91(4):635-646. doi:10.1038/clpt.2011.328
4. Afif W, Loftus EV Jr, Faubion WA, et al: Clinical utility of measuring infliximab and human anti-chimeric antibody concentrations in patients with inflammatory bowel disease. Am J Gastroenterol. 2010;105(5):1133-1139. doi:10.1038/ajg.2010.9
5. Imaeda H, Bamba S, Takahashi K, et al. Relationship between serum infliximab trough levels and endoscopic activities in patients with Crohn's disease under scheduled maintenance treatment. J Gastroenterol. 2014;49(4):674-682. doi:10.1007/s00535-013-0829-7
6. Steenholdt C, Bendtzen K, Brynskov J, Thomsen OO, Ainsworth MA.: Cut-off levels and diagnostic accuracy of infliximab trough levels and anti-infliximab antibodies in Crohn's disease. Scand J Gastroenterol. 2011;46(3):310-318. doi:10.3109/00365521.2010.536254
7. Syversen SW, Jorgensen KK, Goll GL, et al. Effect of Therapeutic Drug Monitoring vs Standard Therapy During Maintenance Infliximab Therapy on Disease Control in Patients With Immune-Mediated Inflammatory Diseases: A Randomized Clinical Trial. JAMA. 2021;326(23):2375-2384. doi:10.1001/jama.2021.21316
8. Feuerstein JD, Nguyen GC, Kupfer SS, Falck-Ytter Y, Singh S; American Gastroenterological Association Institute Clinical Guidelines Committee. American Gastroenterological Association Institute guideline on therapeutic drug monitoring in inflammatory bowel disease. Gastroenterology. 2017;153(3):827-834. doi:10.1053/j.gastro.2017.07.032
9. Silva-Ferreira F, Afonso J, Pinto-Lopes P, Magro F. A systematic review on infliximab and adalimumab drug monitoring: Levels, clinical outcomes and assays. Inflamm Bowel Dis. 2016;22(9):2289-2301. doi:10.1097/MIB.0000000000000855
10. Willrich MA, Murray DL, Barnidge DR, Ladwig PM, Snyder MR. Quantitation of infliximab using clonotypic peptides and selective reaction monitoring by LC-MS/MS. Int Immunopharmacol. Sep 2015;28(1):513-20. doi:10.1016/j.intimp.2015.07.007
11. 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
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)
Monday through Friday
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.
80230
82397-(if appropriate)
| 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
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 63000 | Infliximab, S | 39803-2 |
| 36847 | Interpretation | 59462-2 |