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Order Code LAB1135 Tobramycin, Random, Serum

Additional Codes

MAYO CODE TOBRA

Useful For

Monitoring adequacy of serum concentration during tobramycin therapy

 

This unit code is used whenever a specimen is submitted or collected without collection timing information. The phlebotomist should use this unit code if she or he does not know if this is a peak or trough specimen.

Method Name

Immunoassay

Reporting Name

Tobramycin, Random, S

Specimen Type

Serum


Ordering Guidance


Serum for a peak level should be drawn 30 to 60 minutes after last dose (order TOBPA / Tobramycin, Peak, Serum).

 

Serum for a trough level should be drawn no more than 30 minutes before next scheduled dose (order TOBTA / Tobramycin, Trough, Serum).



Specimen Required


Preferred: Serum gel

Acceptable: Red top

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 aliquoted within 2 hours of collection.


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject

Reference Values

TOBRAMYCIN, PEAK

Therapeutic: 3.0-12.0 mcg/mL

Toxic: >12.0 mcg/mL

 

TOBRAMYCIN, TROUGH

Therapeutic: <2.0 mcg/mL

Toxic: >2.0 mcg/mL

Method Description

The assay is based on a homogeneous enzyme immunoassay technique used for the quantitative analysis of tobramycin in human serum or plasma. The assay is based on competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PDH) 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 G6PDH does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay.(Package insert: Roche Tobramycin reagent, Roche Diagnostic Corp, Indianapolis, IN)

Day(s) Performed

Monday through Sunday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

80200 

Forms

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