Ustekinumab Level and Anti-Ustekinumab Antibody

Label Mnemonic:	USTEK
Epic code:	LAB8602
Downtime form:	Doctor/Provider Orders - Pathology Core and Specialty Care Nursery

Commercial Mailout Laboratory
6240-8 RCP
356-8593

Specimen(s):

Serum

Collection Medium:

Red top tube 5 mL (Clot Activator)

Minimum:

Preferred Minimum: 0.5 mL serum in red top tube.
Absolute Minimum: 0.35 mL serum in red tube.

This test needs its own dedicated tubes and cannot be shared with any other tests. Please submit full draw.

Turn Around Time:

2 days upon receipt at reference laboratory. To avoid delays in turnaround time when requesting multiple tests, please submit separate frozen specimens for each test requested.

Reference Range:

USTEKINUMAB QUANT, SERUM:
Limit of quantitation is 0.3 mcg/mL

In inflammatory bowel disease, at post-induction measurement (week 8), concentrations above3.5 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

Interpretive Data:

                 Antibodies to ustekinumab    ATU present
                 (ATU) absent                 
----------------------------------------------------------------------
                 For nonresponders:           For nonresponders:
                 Insufficient ustekinumab     Insufficient ustekinumab
                 is present. In the absence   is present. Antibodies-
Ustekinumab      of ATU, consider optimizing  to-ustekinumab detected
quantification   therapy by increasing the    can contribute to faster
<1.0 mcg/mL      dose or shortening the       clearance of ustekinumab
                 administration intervals,    and treatment failure.
                 or by adding an immuno-      Clinical evaluation is
                 modulator to the             recommended.
                 therapeutic regimen.         

                 For nonresponders:           For nonresponders:
                 If the sample was collected  If the sample was
                 at trough ie, immediately    collected at trough ie,
Ustekinumab      before the next infusion,    immediately before the
quantification   the results could suggest a  next infusion, the
> or =1.0        mechanistic failure of       results could suggest a
                 ustekinumab. The provider    mechanistic failure of 
                 may consider switching       ustekinumab. The provider
                 therapeutic regimen outside  may consider switching 
                 of the drug class.           therapeutic regimen outside
                                              of the drug class.

Comments:

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

Cautions:
This assay measures free ustekinumab. This assay does not measure ustekinumab bound to anti-ustekinumab antibodies (immunocomplexes).

Presence of ustekinumab at concentrations greater than 1 mcg/mL may impair detection of antibodies to ustekinumab (ATU), as the ATU assay is not drug tolerant. This assay measures free ATU. This assay does not measure ATU bound to UTK (immunocomplexes).

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.

Methodology:

Enzyme-Linked Immunosorbent Assay (ELISA)

CPT Code:

80299, 83520