Test Id : GUS
Guselkumab, Serum
Useful For
Suggests clinical disorders or settings where the test may be helpful
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
A short description of the method used to perform the test
Liquid Chromatography Mass Spectrometry (LC-MS)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Guselkumab
Tremfya
Specimen Type
Describes the specimen type validated for testing
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
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
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.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.25 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | OK |
| Lipemia | Reject |
| Gross icterus | OK |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 28 days | |
| Ambient | 24 hours | ||
| Frozen | 28 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
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
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Guselkumab (Tremfya; Johnson and Johnson) is a fully human IgG1 lambda therapeutic monoclonal antibody used for the treatment of moderate to severe ulcerative colitis (UC), plaque psoriasis, and psoriatic arthritis. Guselkumab targets interleukin (IL) 23A (IL-23p19) binding with high affinity to the p19 subunit and inhibiting further action. In the future, approval by the US Food and Drug Administration (FDA) is expected for the treatment of Crohn disease, broadening the FDA-approved indications for use of this drug.
Therapeutic drug monitoring (TDM) has become standard of care in the gastroenterology practice for biologic therapies used in inflammatory bowel disease (IBD), Crohn disease, and UC. TDM is routinely used to assess loss of response to therapy and proactively manage patients taking tumor necrosis factor inhibitors (eg, infliximab and adalimumab), alpha-4-beta7 integrins (vedolizumab), IL12/23 blockers (ustekinumab). With the approval of guselkumab for IBD, TDM is expected to play an important role in managing loss of response to therapy and guide decision making for use of monotherapy or combination therapy.
The dosing of guselkumab varies according to the condition it is prescribed to treat. Patients with psoriatic arthritis and plaque psoriasis receive 100 mg subcutaneously at weeks 0 and 4 and every 8 weeks thereafter. Patients with ulcerative colitis are treated with 3 intravenous infusions of 200 mg each at weeks 0, 4, and 8, followed by 100 mg or 200 mg subcutaneously at week 12 and every 4 weeks thereafter. Mean steady state trough serum guselkumab concentration was 1.2 mcg/mL in both psoriatic arthritis and plaque psoriasis patients, while UC mean steady-state trough concentrations were 1.4 and 10.7 mcg/mL, with 100 mg and 200 mg dose at maintenance stage, respectively.
Guselkumab is immunogenic, like other therapeutic monoclonal antibodies. Clinical trials have shown antibodies-to-guselkumab occur at rates of about 6% to 9% for plaque psoriasis, 2% for psoriatic arthritis, and 11% for UC.
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Lower limit of quantitation = 0.5 mcg/mL
Interpretation
Provides information to assist in interpretation of the test results
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.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Lipemic samples will be rejected.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Tremfya (guselkumab). Package insert. Johnson and Johnson; 2017. Updated March 2025. Accessed May 19, 2025. Available at www.janssenlabels.com/package-insert/product-monograph/prescribing-information/TREMFYA-pi.pdf
2. 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
3. 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
4. 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
5. 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
6. 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
Method Description
Describes how the test is performed and provides a method-specific reference
Guselkumab is extracted from serum and measured by liquid chromatography mass spectrometry.(Unpublished Mayo method)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Wednesday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
80299
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| GUS | Guselkumab, S | In Process |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 622837 | Guselkumab, S | In Process |