Test ID: TOPI
Topiramate, Serum
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Monitoring serum concentrations of topiramate, particularly in patients with renal disease or those coadministered phenytoin or carbamazepine
Assessing compliance
Assessing potential toxicity
Method Name A short description of the method used to perform the test
Enzyme-Multiplied Immunoassay Technique (EMIT)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Topiramate (Topamax)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Collection Container/Tube: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | Mild OK; Gross reject |
| Icterus | Mild OK; Gross reject |
| Other | Serum gel tube |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Frozen (preferred) | 14 days |
| Refrigerated | 7 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Topiramate is a broad spectrum, anti-epileptic drug used to for various types of seizures, Lennox-Gastaut syndrome (a type of childhood onset epilepsy), and migraine prophylaxis. Topiramate blocks sodium channels, potentiates gamma-aminobutyric acid (GABA) activity, and inhibits potentiation of the glutamate receptor, allowing the drug to block seizure spread. Topiramate shows favorable pharmacokinetics, with good absorption, low protein binding, and minimal metabolism. Elimination is predominantly renal as unaltered topiramate, with an elimination half-life of 20 to 30 hours.
Serum concentrations of other anticonvulsant drugs are not significantly affected by the concurrent administration of topiramate, with exception in individual patients on phenytoin exhibiting increased phenytoin plasma concentrations after addition of topiramate. Coadministration of phenytoin or carbamazepine decreases topiramate serum concentrations. Changes in co-therapy with phenytoin or carbamazepine for patients stabilized on topiramate therapy may require dose adjustment due to these instructions; therapeutic drug monitoring can assist this. As with other renally eliminated anticonvulsant drugs, patients with impaired renal function exhibit decreased topiramate clearance.
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.
2.0-20.0 mcg/mL
Interpretation Provides information to assist in interpretation of the test results
Most individuals display optimal response to topiramate with serum levels 2.0 to 20.0 mcg/mL. Some individuals may respond well outside of this range, or may display toxicity within the therapeutic range, thus interpretation should include clinical evaluation.
Toxic levels have not been well established.
Therapeutic ranges are based on specimens drawn at trough (ie, immediately before the next dose).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test cannot be performed on whole blood.
Serum must be separated from cells within 2 hours of drawing.
Specimens that are obtained from gel tubes are not acceptable.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Patslos PN, Berry DJ, Bourgeois BF, et al: Antiepileptic drugs-best practice guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Epilepsia 2008 Jul;49(7):1239-1276
2. Johannessen SI, Tomsom T: Pharmacokinetic variablility of newer antiepileptic drugs: when is monitoring needed? Clin Pharmacokinet 2006;45(11):1061-1075
3. Snozek CL, Rollins LA, Peterson PW, Langman LJ: Comparison of a new serum topiramate immunoassay to fluorescence polarization immunoassay. Ther Drug Monit 2010 Feb;32(1):107-111
Method Description Describes how the test is performed and provides a method-specific reference
Homogeneous immunoassay based on competition between drug in the specimen, and topiramate labeled with the enzyme glucose-6-phosphate dehydrongenase (G6PDH), for binding to the antibody reagent.(Package insert: ARK Topiramate Assay. ARK Diagnostics Inc., Sunnyvale, CA)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Sunday; Varies
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
80201
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 81546 | Topiramate, S | 17713-9 |
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