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Test Code GUSAP Guselkumab Quantitation with Antibodies, Serum


Specimen Required


Patient Preparation: For 12 hours before specimen collection, patient should not take multivitamins or dietary supplements (eg, hair, skin, and nail supplements) containing biotin (vitamin B7).

Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1.1 mL serum

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

Evaluation of patients with limited primary (initial) response to or secondary loss of response to guselkumab.

Profile Information

Test ID Reporting Name Available Separately Always Performed
GUS Guselkumab, S Yes Yes
GUSAB Guselkumab Ab, S No Yes

Method Name

GUS: Liquid Chromatography Mass Spectrometry (LC-MS)

GUSAB: Electrochemiluminescent Bridging Immunoassay (ECLIA)

Reporting Name

Guselkumab QN with Antibodies, S

Specimen Type

Serum

Specimen Minimum Volume

Serum: 0.75 mL

Specimen Stability Information

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

Reference Values

GUSELKUMAB QUANTITATION:

Guselkumab lower limit of quantitation = 0.5 mcg/mL

 

ANTIBODIES TO GUSELKUMAB:

<9.8 ng/mL

Interpretation

The presence of detectable anti-guselkumab antibodies may be associated with increased guselkumab clearance and lower circulating concentrations of guselkumab in serum. Low trough concentrations of guselkumab may be correlated with loss of response to the drug.

Clinical Reference

1. Janssen Biotech, Inc. Highlights of prescribing information: Tremfya (guselkumab) 2017. Updated September 2025. Accessed October 2, 2025. Available at www.janssenlabels.com/package-insert/product-monograph/prescribing-information/TREMFYA-pi.pdf

2. The efficacy and safety of guselkumab induction therapy in patients with moderately to severely active ulcerative colitis: Results from the Phase 3 QUASAR Induction Study. Gastroenterol Hepatol (N Y). 2023;19(7 Suppl 3):9-10

3. Peyrin-Biroulet L, Allegretti JR, Rubin DT, et al. Guselkumab in patients with moderately to severely active ulcerative colitis: QUASAR Phase 2b Induction Study. Gastroenterology. 2023;165(6):1443-1457. doi:10.1053/j.gastro.2023.08.038

4. Danese S, Panaccione R, Feagan BG, et al. Efficacy and safety of 48 weeks of guselkumab for patients with Crohn’s disease: maintenance results from the phase 2, randomized, double-blind GALAXI-1 trial. Lancet Gastroenterol Hepatol. 2024;9(2):133-146

5. Shao J, Vetter M, Vermeulen A, et al. Combination therapy with guselkumab and golimumab in patients with moderately to severely active ulcerative colitis: Pharmacokinetics, immunogenicity and drug-drug interactions. Clin Pharmacol Ther. 2024;115(6):1418-1427

6. Ladwig PM, Barnidge DR, Willrich MA. Quantification of the IgG2/4 kappa monoclonal therapeutic eculizumab from serum using isotype specific affinity purification and microflow LC-ESI-Q-TOF mass spectrometry. J Am Soc Mass Spectrom. 2017;28(5):811-817

7. Ladwig PM, Barnidge DR, Willrich MAV. Mass spectrometry approaches for identification and quantitation of therapeutic monoclonal antibodies in the clinical laboratory. Clin Vaccine Immunol. 2017;24(5):e00545-16

8. Sharma K, da Silva BC, Hanauer SB. The role of immunogenicity in optimizing biological therapies for inflammatory bowel disease. Expert Rev Gastroenterol Hepatol. 2025;19(3):243-258

Day(s) Performed

Weekly

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

83520

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GUSAP Guselkumab QN with Antibodies, S In Process

 

Result ID Test Result Name Result LOINC Value
622837 Guselkumab, S In Process
623122 Guselkumab Ab, S In Process
623291 GUSAB Interpretation 77202-0