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Test Code LAB0248629 Infliximab Quantitation with Reflex to Antibodies to Infliximab, Serum

Additional Codes

 

Mayo Test ID
INFXR

 

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful 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

 

This test does not differentiate between the originator and biosimilar products.

Testing Algorithm

Infliximab quantitation 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

Method Name

INFXR, INFX: Selective Reaction Monitoring Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

INXAB: Electrochemiluminescent Bridging Immunoassay with Acid Dissociation

Reporting Name

Infliximab QN with Reflex to Ab, S

Specimen Type

Serum Red


Specimen Required


Patient Preparation:

1. Draw blood immediately before next scheduled dose (trough specimen).

2. For 12 hours before specimen collection, patient should not take multivitamins or dietary supplements (eg, hair, skin, and nail supplements) containing biotin (vitamin B7).

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL Serum

Collection Instructions: Within 2 hours of collection, centrifuge and aliquot serum into plastic vial.


Specimen 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

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 (IFX) due to possible development of an immune response to IFX. Testing for antibodies-to-infliximab (ATI) is suggested in patients with trough concentrations less than or equal to 5.0 mcg/mL.

 

Infliximab trough concentrations greater 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 greater than or equal to 35 mcg/mL suggest possible testing at a time point other than trough if intravenous 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), results of other laboratory tests, and a combination of the drug concentration and 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.

 

Infliximab quantitation, mcg/mL

Antibodies-to-infliximab, U/mL

Comment

<5

Negative

Absence of detectable antibodies-to-infliximab (ATI). Low concentration of infliximab (IFX) may be attributable to other parameters related to IFX clearance.

<5

Positive

Presence of ATI detected, which correlates with low concentration of IFX. 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.

5-10

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.

5-10

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.

>10

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.

>10

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

Monday through Friday

Report Available

3 to 6 days

Specimen Retention Time

2 weeks

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

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

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

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)