Test Directory

• Ustekinumab Quantitation
• Ustekinumab Antibodies

Useful for the evaluation of loss of response to therapy, quantification of ustekinumab in human serum, trough level quantitation for evaluation of patients treated with ustekinumab, and the detection of antibodies to ustekinumab in human serum.

Specimen Type: Serum

Preferred Collection Container: Gold Top, Serum Separator

Alternate Collection Container: Red Top, Plain

Desired Specimen Volume: 0.5 mL

1. Collect a gold top, serum separator tube via venipuncture.

1. Separate serum from cells.
2. Transfer 0.5 mL of serum to a clear aliquot tube (screw cap).

Collect immediately before the next dose of drug administration (trough level).

Transport to the laboratory refrigerated. 

• Heat-inactivated specimen

See patient report.

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

• Stelara
• Stelara antibodies