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HelpEpic Test Code LAB1853 Ustekinumab Quantitation with Antibodies, Serum
Additional Codes
MML:USTEK
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, SSpecimen Type
SerumSpecimen 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: |
For nonresponders: |
|
Ustekinumab quantification ≥1.0 mcg/mL |
For nonresponders: |
For nonresponders: |
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 daysSpecimen Retention Time
14 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
80299
83520
NY State Approved
YesTesting Algorithm
For more information see Ulcerative Colitis and Crohn Disease Therapeutic Drug Monitoring Algorithm.