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Test Code TOBTR.MY Tobramycin, Trough, Serum

Additional Codes

TOBTA

Useful For

Monitoring adequate clearance of tobramycin near the end of a dosing cycle

Method Name

Immunoassay

Reporting Name

Tobramycin, Trough, S

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Draw blood no more than 30 minutes before next scheduled dose.

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

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


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

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

Reject Due To

Gross hemolysis Reject

Clinical Information

Tobramycin is an antibiotic used to treat life-threatening blood infections by gram-negative bacilli, particularly Citrobacter freundii, Enterobacter (all species), Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Providencia stuartii, Pseudomonas aeruginosa, and Serratia species. It is often used in combination with beta-lactam therapy.

 

A tobramycin minimum inhibitory concentration (MIC) of less than 4.0 mcg/mL is considered susceptible for gram-negative bacilli, while a MIC of greater than 8.0 mcg/mL is considered resistant.

 

Toxicities include ototoxicity and nephrotoxicity. This risk is enhanced in presence of other ototoxic or nephrotoxic drugs. Monitoring of serum levels, renal function, and symptoms consistent with ototoxicity is important. For longer durations of use, audiology and vestibular testing should be considered at baseline and periodically during therapy.

Reference Values

Therapeutic: <2.0 mcg/mL

Toxic: >2.0 mcg/mL

Interpretation

Goal levels depend on the type of infection being treated. Goal trough levels should be below 2.0 mcg/mL for conventional (nonpulse) dosing. Prolonged exposure to trough levels exceeding 2.0 mcg/mL may lead to toxicity.

Cautions

No significant cautionary statements

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 to 2 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

80200

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TOBTA Tobramycin, Trough, S 4059-2

 

Result ID Test Result Name Result LOINC Value
TOBTA Tobramycin, Trough, S 4059-2

Forms

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