Infliximab and Antibodies to Infliximab Quantitation

Also known as: IFX PAN

Clinical Use

Use

This test is used to monitor infliximab or infliximab biosimilar therapy. It is particularly relevant for patients undergoing treatment for conditions such as Inflammatory Bowel Disease (IBD) and Rheumatoid Arthritis (RA). The test measures both the concentration of infliximab in the serum and the presence of antibodies against infliximab, which can affect the efficacy of the treatment. The results are crucial for adjusting the therapeutic regimen to ensure optimal therapeutic levels and to evaluate the potential development of resistance due to antibodies against the drug.

Special Instructions

Not provided.

Limitations

The test's quantitative limits are significant for interpretation. For infliximab quantitation, a level of 0.5 ug/mL or higher indicates detection of the drug or its biosimilar, but therapeutic levels may vary depending on the disease. Similarly, antibody levels of 20 ng/mL or higher suggest the presence of antibodies against infliximab. However, the presence of antibodies should be interpreted in the context of infliximab trough concentration to determine clinical significance and impact on treatment efficacy. This test has not been cleared or approved by the U.S. Food and Drug Administration but is developed following CLIA guidelines.

Test Details

New York Approved

Methodology

Immunoassay (ECLIA)

Biomarkers

2 components

Infliximab Quantitation • ECLIAAntibodies to Infliximab Quantitation • ECLIA

LOINC Codes

Result Codes

86896-8 - inFLIXimab SerPl IA-mCnc
86897-6 - inFLIXimab Ab SerPl IA-mCnc

Result Turnaround Time

3-7 days

Specimen

Serum

Volume

1 mL

Minimum Volume

0.1 mL

Container

Serum separator tube

Collection Instructions

Separate serum from cells ASAP after collection. Transfer 1 mL serum to an ARUP standard transport tube.

Patient Preparation

Collect specimen before the next scheduled dose of infliximab or infliximab biosimilar (trough specimen). Avoid exposure to biotin (vitamin B7) for 12 hours prior to specimen collection.