Ustekinumab Quantitation with Antibodies, Serum
Test Mnemonic
USTEKQ
CPT Codes
- 80299 - QTY (1)
- 83520 - QTY (1)
Aliases
- Stelara
Includes
- Ustekinumab QN, S
- Ustekinumab Ab, S
Performing Laboratory
Mayo Clinic Dpt of Lab Med & Pathology
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.5 mL | Serum | SST (Gold) | Refrigerated | Collect immediately before the next dose of drug administration (trough level). Separate serum from cells and transfer to standard aliquot tube. |
Alternate Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.5 mL | Serum | No additive (Red) | Refrigerated | Collect immediately before the next dose of drug administration (trough level). Separate serum from cells and transfer to standard aliquot tube. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.35 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Refrigerated | 3 weeks |
| Frozen | 3 weeks |
| Ambient | Unacceptable |
Days Performed
Mon, Wed, Fri
Turnaround Time
3 - 6 days
Methodology
| Name | Description |
|---|---|
| Enzyme-Linked Immunosorbent Assay (ELISA) |
Reference Range
Special Info
Collect immediately before the next dose of drug administration (trough level). Heat-inactivated specimens will be rejected. This test is New York State approved.
Clinical Info
This assay measures free ustekinumab (UTK) and free antibodies to ustekinumab (ATU). 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. 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 > or =1.0 mcg/mL are associated with clinical response and clinical remission; Concentrations > or =4.5 mcg/mL are associated with mucosal healing. USTEKINUMAB AB, S: Limit of quantitation is 10 AU/mL. Absent: <10 AU/mL; Present: > or =10 AU/mL
Clinical Limitation
This assay does not measure immunocomplexes of UTK bound to antibodies-to-ustekinumab (ATU). 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.