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Test Code LAB683 Ethosuximide, Serum

Additional Codes

ETX


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. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.


Secondary ID

8769

Useful For

Monitoring ethosuximide therapy

 

Determining compliance

 

Assessing ethosuximide toxicity

Method Name

Enzyme-Multiplied Immunoassay Technique (EMIT)

Specimen Type

Serum

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  28 days
  Ambient  14 days

Reject Due To

Gross hemolysis Reject

Reference Values

Therapeutic: 40-100 mcg/mL

Critical value: >150 mcg/mL

Interpretation

Dosage is guided by blood levels; the therapeutic range for ethosuximide is 40 to 100 mcg/mL.

 

Toxic concentration: above 120 mcg/mL.

Method Description

The enzyme-multiplied immunoassay technique assay is a homogeneous enzyme immunoassay technique used for the analysis of specific compounds in biological fluids. The assay is based on competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PD) for antibody binding sites. Enzyme activity decreases upon binding to the antibody, so the drug concentration in the sample can be measured in terms of enzyme activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD) to NADH, resulting in an absorbance change that is measured spectrophotometrically. Endogenous serum G6PD does not interfere, because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay.(Package insert: Ethosuximide reagent. Siemens Healthcare Diagnostics, Inc; 04/2015)

Day(s) Performed

Monday through Saturday

Report Available

Same day/1 day

Specimen Retention Time

2 weeks

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

80168

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ETX Ethosuximide, S 3616-0

 

Result ID Test Result Name Result LOINC Value
8769 Ethosuximide, S 3616-0

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Therapeutics Test Request (T831)

-Neurology Specialty Testing Client Test Request (T732)