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Test Code GUS Guselkumab, Serum


Ordering Guidance


Therapeutic drug monitoring of guselkumab may be useful when assessing response to therapy is difficult or when patients need to be above a certain therapeutic concentration to improve the odds of a clinical response for therapy optimization, dose increases, or de-escalation or discontinuation of therapy.



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 next scheduled dose (trough specimen).

2. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.


Useful For

Assessing the response to guselkumab therapy

 

Assessing the need for dose escalation

 

Evaluating the potential for dose de-escalation or discontinuation of therapy

 

Monitoring patients who need to be above a certain guselkumab concentration to improve the odds of a clinical response for therapy optimization

Method Name

Liquid Chromatography Mass Spectrometry (LC-MS)

Reporting Name

Guselkumab, S

Specimen Type

Serum

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  24 hours

Reject Due To

Gross hemolysis OK
Lipemia Reject
Gross icterus OK

Reference Values

Lower limit of quantitation = 0.5 mcg/mL

Interpretation

The optimal therapeutic concentration of guselkumab associated with favorable outcomes in inflammatory bowel disease is not known at this time. In ulcerative colitis, the recommendation is to use the lowest concentration that maintains response. The approved dosing regimen for ulcerative colitis involves an initial induction phase with intravenous infusions followed by maintenance doses with subcutaneous injections. According to the guselkumab package insert, mean steady-state trough serum guselkumab concentration ranged from 1.2 to 10.7 mcg/mL, depending on the dosing regimen used.(1)

 

Other therapeutic thresholds vary according to the disease, treatment regimen, and response or lack of response to therapy.

Day(s) Performed

Wednesday

Report Available

2 to 9 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80299

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GUS Guselkumab, S In Process

 

Result ID Test Result Name Result LOINC Value
622837 Guselkumab, S In Process