Rituximab and Anti-Rituximab Antibody, DoseASSURE™ RTX

TEST: 504355
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CPT: 80299, 82397
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Test Includes

All positive antibody results are verified by confirmatory test.

Expected Turnaround Time

4 - 14 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Serum

Volume

3 mL

Minimum Volume

1 mL (Note: this volume does not allow for repeat testing.)

Container

Serum-gel tube, red-top tube or serum transfer tube

Collection

Serum must be separated from cells within 45 minutes of venipuncture. Submit serum in a plastic transport tube. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Refrigerate or freeze

Stability Requirements

Temperature Period Room temperature 7 days Refrigerated 14 days Frozen 14 days Freeze/thaw cycles Stable x6

Causes for Rejection

Gross hemolysis; gross lipemia; icteric specimen

Test Details

Use

Therapeutic monitoring of rituximab and antidrug antibody development for individuals with non-Hodgkin’s lymphoma (NHL), chronic lymphocytic leukemia (CLL), and rheumatoid arthritis. This test provides rituximab drug concentration as well as the level of antirituximab antibodies.

Limitations

Failure of rituximab therapy may not always be due to the presence of anti-rituximab antibodies. Conversely, the absence of anti-rituximab antibodies does not guarantee positive response to treatment. This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration. High serum biotin concentrations in patients taking biotin supplements may cause an interference in this assay. Patients may be advised to stop biotin consumption at least 72 hours prior to sample collection.

Methodology

Electrochemiluminescence immunoassay (ECLIA); chemiluminescence immunoassay (CLIA)

Reference Interval

Rituximab drug level: Quantitation limit: <2.0 μg/ mL. Result of ≥2.0 μg/mL indicates detection of rituximab. In the presence of anti-rituximab antibodies, the rituximab drug level reflects the antibody unbound fraction of serum rituximab concentration. Anti-rituximab antibody: Quantitation limit: <25 ng/mL. A result of ≥ 25 ng/mL indicates detection of anti-rituximab antibodies.