Test Catalog

Test Id : MTXSG

Methotrexate Post Glucarpidase, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

Monitoring methotrexate concentrations postglucarpidase therapy

Method Name
A short description of the method used to perform the test

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Methotrexate Post Glucarpidase, S

Specimen Type
Describes the specimen type validated for testing

Serum

Shipping Instructions

Ship specimen in amber vial to protect from light.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Supplies: Amber Frosted Tube, 5 mL (T192)

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Amber vial

Specimen Volume: 1 mL

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.2 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK
Exposed to light >24 hours Reject

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) 7 days LIGHT PROTECTED
Frozen 14 days LIGHT PROTECTED
Ambient 7 days LIGHT PROTECTED

Useful For
Suggests clinical disorders or settings where the test may be helpful

Monitoring methotrexate concentrations postglucarpidase therapy

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Methotrexate, an antimetabolite (folate reductase inhibitor), is used at high dose (12 gm/m[2]) to treat neoplastic diseases, such as lymphocytic leukemia. Therapy is guided by measurement of serum concentration: 24 hours after dosage, the serum concentration should be less than 10 mcmol/L; 48 hours after dosage, concentration should be less than 1 mcmol/L; and 72 hours after dosage, the concentration should be less than 0.1 mcmol/L or less than 0.05 mcmol/L, depending on clinical protocol. It is also administered at low dose (a single dose of 5-15 mg per week) to treat severe psoriasis and rheumatoid arthritis. Methotrexate is 65% orally bioavailable. Peak serum concentrations are reached 2 to 3 hours after dosing. Protein binding is approximately 45%. Volume of distribution is 0.4 L/kg. Elimination is concentration dependent with an apparent elimination half-life of 1.8 hours when the serum concentration is above 1 mcmol/L, 8 hours when between 0.1 and 1 mcmol/L, and approximately 30 hours when below 0.1 mcmol/L.

 

Voraxaze (glucarpidase) is a carboxypeptidase enzyme indicated for the treatment of toxic plasma methotrexate (MTX) concentrations (>1 mcmol/L) in patients with delayed methotrexate clearance due to impaired renal function. Measurement of methotrexate using immunoassays is unreliable for specimens collected within 48 hours following Voraxaze administration since it can result in falsely elevated results. As a result, this liquid chromatography-tandem mass spectrometry assay should be used to monitor MTX concentrations postglucarpidase therapy.

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.

Nontoxic drug concentration after 72 hours: <0.1 mcmol/L

Interpretation
Provides information to assist in interpretation of the test results

Following a 4 to 6 hour intravenous infusion of methotrexate, postinfusion concentrations greater than the following indicate an increased risk of toxicity if conventional low-dose leucovorin rescue is given:

-24-hour postinfusion concentration: 5.0 to 10.0 mcmol/L

-48-hour postinfusion concentration: 0.5 to 1.0 mcmol/L

-72-hour postinfusion concentration: 0.1 mcmol/L

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

The specimen must be protected from light.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Cadman EC, Durivage HJ: Cancer chemotherapy: alkylating agents. In: Wilson JD, Braunwald E, Isselbacher KJ, eds. Harrison's Principles of Internal Medicine. 12th ed. McGraw-Hill Book Company; 1991: 1592-1594

2. Jameson JL, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J, eds: Harrison's Principles of Internal Medicine. 20th ed. McGraw-Hill Education; 2018

Method Description
Describes how the test is performed and provides a method-specific reference

Methotrexate is isolated from serum using methanol extraction. Analysis is performed by liquid chromatography-mass spectrometry/mass spectrometry using selected ion monitoring.(Package insert: Voraxaze [Glucarpidase]. BTG International Inc; 2012)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

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.

Monday through Sunday

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.

Same day/1 day

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

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 Regional Manager. 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. This test 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.

80204

LOINC® Information

Test Id Test Order Name Order LOINC Value
MTXSG Methotrexate Post Glucarpidase, S 51602-1
Result Id Test Result Name Result LOINC Value
Result LOINC Value Tooltip
62580 Methotrexate Post Glucarpidase, S 51602-1

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports