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Test Code Billings Clinic: 7602 Mayo: INFXR Infliximab Quantitation with Reflex to Antibodies to Infliximab, Serum

Reporting Name

Infliximab QN with Reflex to Ab, S

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Trough level quantitation for evaluation of patients undergoing therapy with infliximab, with signs and symptoms of loss of response to therapy.

Method Name

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

INXAB: Electrochemiluminescent Bridging Immunoassay with Acid Dissociation


Specimen 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.


Specimen Type

Serum Red

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.

Day(s) Performed

Monday through Friday

Report Available

3 to 6 days

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

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)

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