Test Catalog

Test Id : TCZ

Tocilizumab Quantitation, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

Quantitation of tocilizumab in patients receiving this therapy

Method Name
A short description of the method used to perform the test

Electrochemiluminescent Bridging Immunoassay

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Tocilizumab QN, S

Lists additional common names for a test, as an aid in searching



Cytokine release syndrome


Specimen Type
Describes the specimen type validated for testing


Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: For 12 hours before specimen collection, patients should not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.


Preferred:  Serum gel

Acceptable: Red top

Specimen Volume: 0.6 mL

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK
Heat-treat specimen Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
Frozen 28 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Quantitation of tocilizumab in patients receiving this therapy

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Tocilizumab is a recombinant humanized IgG1 kappa monoclonal antibody that targets the interleukin-6 (IL-6) receptor. By binding soluble and membrane-bound IL-6 receptors, it blocks the pro-inflammatory effects of IL-6 mediated signaling. IL-6 has been shown to be involved in diverse physiological processes such as T-cell activation, induction of immunoglobulin secretion, initiation of hepatic acute phase protein synthesis, and stimulation of hematopoietic precursor cell proliferation and differentiation. Although a critical component of the immune response against infection, IL-6 is an important mediator in many autoimmune diseases. For example, IL-6 is produced by synovial and endothelial cells leading to local production of IL-6 in joints affected by inflammatory processes such as rheumatoid arthritis (RA). Studies in a variety of autoimmune diseases demonstrated that blocking IL-6 led to improved clinical outcomes. Tocilizumab is currently Food and Drug Administration-approved for the treatment of RA (moderate to severe), giant cell arteritis, systemic juvenile idiopathic arthritis (JIA), and polyarticular JIA.


IL-6 is also a critical component of the cytokine release syndrome (CRS). CRS results from an overactive immune response and leads to significantly enhanced expression of multiple inflammatory cytokines. CRS can occur in a variety of situations, including autoimmune disease, infection, and immune therapies. Chimeric antigen receptor (CAR) T-cell therapy is approved for the treatment of large B-cell non-Hodgkin lymphomas and acute lymphoblastic leukemia. In this therapy, the patient's T cells are isolated and genetically engineered to express chimeric antigen receptors, which target the tumor cells. Some patients experience CRS after the engineered T cells are re-administered; in some cases, the magnitude of the CRS can be life-threatening with manifestations including hypotension, tachycardia, and multi-organ failure. Tocilizumab is approved for treatment of CRS associated with CAR T-cell therapy. It is also being investigated for treatment of CRS in other clinical situations.


Pharmacokinetics of tocilizumab is characterized by nonlinear elimination, which is a combination of linear clearance and Michaelis-Menten elimination. The nonlinear part of tocilizumab elimination leads to an increase in exposure that is more than dose proportional. The pharmacokinetic parameters of tocilizumab do not change with time. Due to the dependence of total clearance on tocilizumab serum concentrations, the half-life of tocilizumab is also concentration-dependent and varies depending on the serum concentration level. Population pharmacokinetic analyses in any patient population tested so far indicate no relationship between apparent clearance and the presence of anti-drug antibodies.(1)

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Tocilizumab limit of quantitation =0.5 mcg/mL

Provides information to assist in interpretation of the test results

Measured concentrations of tocilizumab will be impacted by the route of administration, the dosage, and the time interval between drug administration and blood collection. Measured concentrations should be interpreted in the context of the last administered dose of tocilizumab.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Therapeutic concentrations for tocilizumab have not been defined for any of the approved clinical indications.


When present at high concentrations, biotin may interfere with certain immunoassays. For tocilizumab, no interference has been found up to 300 ng/mL of biotin. Serum concentrations greater than 300 ng/mL may be rarely found in patients with poor renal function or taking high-dose biotin supplements daily. It is recommended to avoid biotin use for a minimum of 12 hours prior to having a blood draw for this test.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. ACTEMRA (tocilizaumab). Medication Guide and Instructions for Use. Genetech, Inc; 05/2020. Available at www.gene.com/download/pdf/actemra_prescribing.pdf

2. Tanaka T, Narazaki M, Kishimoto T: IL-6 in inflammation, immunity, and disease. Cold Spring Harb Perspect Biol. 2014;6(10):a016295

3. Sheppard M, Laskou F, Stapleton PP, Hadavi S, Dasgupta B: Tocilizumab (Actemra). Hum Vaccin Immunother. 2017;13(9):1972-1988

Method Description
Describes how the test is performed and provides a method-specific reference

This lab-developed immunoassay is designed to determine tocilizumab (TCZ) (Actemra, Genentech Inc.) concentrations in human serum by means of electrochemiluminescence (ECL). The assay uses a "bridging" format in which TCZ forms a link between biotin-labeled anti-tocilizumab and Sulfo-Tag labeled anti-tocilizumab. During sample preparation, antibodies to TCZ are added and bind with drug that is present in the sample. After the incubation with the labeled antibodies, the calibrators, controls, and samples are added to a plate. After an incubation period, the plate is washed and read buffer is added. Immediately after the addition of read buffer, the plate is analyzed. The intensity of emitted light is measured and is correlated to a set of standards with known concentrations of TCZ by means of a 4-point logistics curve fitting method.(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday, Thursday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

1 to 5 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

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  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports