Provides ustekinumab drug concentration and anti-ustekinumab antibodies in order to optimize treatment and facilitate clinical decision-making.

This assay may be helpful in any patients on ustekinumab therapy for Crohn's disease, psoriasis, or other autoimmune conditions.

Gold serum separator (SST) tube

OR

Red serum vial/tube - 5 mL

Immediately following collection, mix sample thoroughly by gentle inversion, 5 times

1. Allow sample to clot for a minimum of 30 minutes
2. Spin within two (2) hours of sample collection
3. Transfer serum to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as serum
4. Freeze

Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp)

Lavender (EDTA), 4mL

Dk green heparin (Li or Na), no gel

Lavender/Dk green:

Immediately following collection, mix sample thoroughly by gently inverting 8 - 10 times, to prevent clotting

1. Spin within two (2) hours of sample collection
2. Transfer plasma to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as the appropriate plasma type
3. Freeze

Frozen (preferred) - 14 days

Refrigerated - 14 days

Ambient- 14 days

Freeze/thaw cycles: Stable x 6

Electrochemiluminescence immunoassay (ECLIA)

Ustekinumab: <0.1 μg/mL

• Result ≥0.1 μg/mL indicates detection of ustekinumab
• In the presence of anti-ustekinumab antibodies, the ustekinumab drug level reflects the free, antibody-unbound fraction of ustekinumab in serum.

Anti-ustekinumab antibody: <40 ng/mL

• Result ≥40ng/mL indicates detection of anti-ustekinumab antibodies.

Drug assay:

The ustekinumab drug level typically reflects the antibody-unbound (the free fraction) of ustekinumab when serum anti-ustekinumab antibodies are present. In the absence of anti-ustekinumab antibodies, the ustekinumab drug level typically reflects the total ustekinumab concentration in serum.

Anti-drug antibody assay:

This anti-ustekinumab antibody assay is “drug-tolerant,” that is, the presence of serum ustekinumab does not impede the detection and quantitation of anti-ustekinumab antibodies. This anti-ustekinumab antibody assay is specific; antibodies against other biologic drugs do not cross-react with this assay. All positive anti-ustekinumab antibody results are verified by a confirmatory test.