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Test Code LAB26 Gentamicin Level, Trough, Blood

Performing Laboratory

St. Louis Children's Hospital - Chemistry

Specimen Requirements

Patient Preparation: None

Container/Tube  
Preferred: Mint green-top Lithium heparin (MNTGRN LiHep) tube
Acceptable: Green samplette/microtainer, plain red-top tube, Lavender-top (EDTA) tube, or Gold SST gel tube

Collection Volume: 1.0 mL (minimum 0.6 mL)

Submission Container/Tube: If specimen is coming from outside facility and collected in a microtainer, Lavender-top (EDTA) tube, or plain red-top tube aliquot processed sample into a plastic vial for transport (labeling with specimen type).
Special Instructions: Specimens should be collected 30 minutes prior to next dose. 

Sample Rejection

Mislabeled or unlabeled specimens

Logistics

Test Availability: Monday-Sunday
Cut-off time: None; performed as received
Turnaround Time: Same day; 2 hours from receipt in performing lab

Reference Values

Therapeutic Range: 

<18 years: ≤ 1.0 mcg/mL
≥ 18 years: ≤ 2.0 mcg/mL                                                                 

Critical Values: >2.0 mcg/mL

Critical test results will be automatically called back initially and every 24 hours thereafter.

Methodology

Particle-enhanced turbidimetric Immunoassay 

Limitations

  • Patient samples which contain the drug sisomicin will yield falsely elevated values for gentamicin.
  • Some samples containing antibodies to E.coli Beta-galactosidase can result in artificially high gentamicin results that do not fit clinical profile. If this occurs, contact lab.
  • As with any assay employing mouse antibodies, the possibility exists for interference by HAMA in the sample, which could cause falsely elevated results.

 

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: Centrifuge specimen to separate. If specimen is collected in a plain, red-top, microtainer, or Lavender-top (EDTA) tube, aliquot sample into a Roche false-bottom tube for testing (labeling with specimen type).
Processed Volume: 0.3 mL plasma/serum
Analyte Stability:

Specimen Type Temperature Time  
Whole Blood (unprocessed)  Ambient 8 hours  
Plasma/Serum (processed) Refrigerated (preferred)   1 week  
  Ambient  8 hours  
  Frozen  2 weeks     
Note: specimen should not be repeatedly frozen and thawed  

Test Classification and CPT Coding

80170

LOINC

3665-7

Last Reviewed

06/2025