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Infliximab Level for Rheumatic Diseases
Test Code36310
CPT Codes
80230
Preferred Specimen
1 mL serum collected in a red-top tube (no gel)
Minimum Volume
0.3 mL
Instructions
The blood should be drawn just before the next infusion of infliximab to measure the trough drug level.
Transport Temperature
Refrigerated (cold packs)
Specimen Stability
Room temperature: 48 hours
Refrigerated: 7 days
Frozen -20°C: 28 days
Frozen -70°C: 70 days
Refrigerated: 7 days
Frozen -20°C: 28 days
Frozen -70°C: 70 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Serum Separator Tube (SST)
Methodology
Enzyme Linked Immunosorbent Assay (ELISA)
FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Setup Schedule
Set up: Mon, Tues, Thurs-Sat; Report available: 2-3 days
Reference Range
See Laboratory Report
Clinical Significance
When treatment of rheumatic diseases with infliximab or its biosimilar fails, a physician may need to consider treatment options, such as adjusting dose or dosing intervals, switching to a different TNF blocker, or switching to a different drug agent, i.e. a non-TNF blocker. This assay specifically measures serum infliximab and infliximab-dyyb (inflectra) levels. Data from clinical studies suggest a target infliximab trough concentration of 2-8 mcg/mL or 2-10 mcg/mL in rheumatoid arthritis. Based on the results of clinical equivalence studies, the FDA and an American College of Rheumatology position statement advocate applying infliximab clinical guidance to the use of its biosimilars.
