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Test Code USTEK Ustekinumab Quantitation with Antibodies, Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Draw blood immediately before the next dose of drug administration (trough level).

2. Centrifuge and aliquot serum into a plastic vial.


Forms

If not ordering electronically, complete, print, and send 1 of the following with the specimen:

-Gastroenterology and Hepatology Test Request (T728)

-Therapeutics Test Request (T831)

Useful For

Evaluation of loss of response to therapy

 

Quantification of ustekinumab in human serum

 

Trough level quantitation for evaluation of patients treated with ustekinumab

 

Detection of antibodies to ustekinumab in human serum

Profile Information

Test ID Reporting Name Available Separately Always Performed
USQN Ustekinumab QN, S No Yes
USTAB Ustekinumab Ab, S No Yes

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Reporting Name

Ustekinumab QN with Antibodies, S

Specimen Type

Serum

Specimen Minimum Volume

0.35 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 21 days
  Frozen  21 days

Reject Due To

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

Clinical Information

Ustekinumab (UTK) is a fully human IgG1 kappa monoclonal antibody (1) that binds with high affinity to the p40 subunit of human interleukin (IL)12 and IL23 and has been approved for the treatment of patients with moderate to severe Crohn disease (CD), moderate to severe ulcerative colitis (UC), psoriatic arthritis, and plaque psoriasis. The drug prevents IL12 and IL23 bioactivity by binding and neutralizing the shared p40 subunit, preventing interaction with the cell surface receptor protein IL12Rbeta1. Through this mechanism of action, UTK effectively neutralizes IL12 and IL23, proteins that are thought to be associated with gastrointestinal inflammation in CD and UC. In the setting of the inflammatory bowel diseases (IBD), CD and UC, the treatment regimen is started with a single weight-based loading dose of the t-mab administered intravenously (IV), and a maintenance regimen with standard (non-weight based) subcutaneous administration of ustekinumab 8 weeks after induction dose, and every 8 weeks thereafter. There is very little data supporting proactive therapeutic drug monitoring for ustekinumab.

 

This test is most useful in the evaluation of loss of response to therapy. A gradual decrease in efficacy over time following an initial response to biologics is common. In many cases, antibodies generated to the biologic are responsible for treatment failure, as they bind to the drug creating an immunocomplex and clear the drug faster from circulation.

 

For IBD, measurements in nonresponders are indicated at post-induction (week 8) and concentrations of ustekinumab associated with favorable outcomes are greater than 3.5 mcg/mL. In addition, for measurements during maintenance stages of therapy, ustekinumab concentrations greater than or equal to 1 mcg/mL are associated with clinical response and clinical remission. At maintenance stages, ustekinumab concentrations greater than or equal to 4.5 mcg/mL are associated with mucosal healing.

 

In clinical trials, 6% to 12.4% of patients using ustekinumab for psoriasis or psoriatic arthritis developed antibodies-to-ustekinumab (ATU) over time. For IBD, between 2.9% and 4.6% of patients developed ATU when treated with ustekinumab for 1 year.(1) Therefore, it is important to monitor trough concentrations of serum UTK to correlate drug levels with loss of response to therapy. ATU may increase drug clearance in treated patients or neutralize the drug effect, thereby potentially contributing to the loss of response. ATU could also cause adverse events, such as serum sickness and hypersensitivity reactions.

 

Currently, ustekinumab quantitation is performed in conjunction with immunogenicity assessment for ATU.

Reference Values

USTEKINUMAB QN, S:

Limit of quantitation is 0.3 mcg/mL

 

In inflammatory bowel disease, at post-induction measurement (week 8), concentrations above 3.5 mcg/mL are associated with good outcomes.

 

For maintenance stages:

Concentrations ≥1.0 mcg/mL are associated with clinical response and clinical remission

Concentrations ≥4.5 mcg/mL are associated with mucosal healing

 

USTEKINUMAB AB, S:

Limit of quantitation is 10 AU/mL

Absent: <10 AU/mL

Present: ≥10 AU/mL

Interpretation

Antibodies to ustekinumab (ATU) absent

ATU present

Ustekinumab quantification

<1.0 mcg/mL

For nonresponders:
Insufficient ustekinumab is present.
In the absence of ATU, consider optimizing therapy by increasing the dose or shortening the administration intervals, or by adding an immunomodulator to the therapeutic regimen.

For nonresponders:
Insufficient ustekinumab is present. Antibodies-to-ustekinumab detected can contribute to faster clearance of ustekinumab and treatment failure. Clinical evaluation is recommended.

Ustekinumab quantification

≥1.0 mcg/mL

For nonresponders:
If the sample was collected at trough ie, immediately before the next infusion, the results could suggest a mechanistic failure of ustekinumab. The provider may consider switching therapeutic regimen outside of the drug class.

For nonresponders:
If the sample was collected at trough ie, immediately before the next infusion, the results could suggest a mechanistic failure of ustekinumab. The provider may consider switching therapeutic regimen outside of the drug class.

Cautions

This assay measures free ustekinumab (UTK) and free antibodies to ustekinumab (ATU). This assay does not measure UTK bound to ATU (immunocomplexes).

 

Presence of UTK at concentrations greater than 1 mcg/mL may impair detection of ATU, as the ATU assay is not drug tolerant.

 

Elevated rheumatoid factor (RF) may falsely increase results of ATU. During validation studies, negative ATU samples remained negative and positive ATU samples remained positive; however, the quantitative result differed by more than 20% when compared to the non-RF spiked original samples. If patients are positive for RF, clinical correlation is recommended for ATU test interpretation.

Day(s) Performed

Monday, Wednesday, Friday

Report Available

2 to 5 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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

80299

83520

LOINC Code Information

Test ID Test Order Name Order LOINC Value
USTEK Ustekinumab QN with Antibodies, S In Process

 

Result ID Test Result Name Result LOINC Value
USQN Ustekinumab QN, S 87408-1
USTAB Ustekinumab Ab, S 87409-9