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Test Code 2541 Gentamicin, Trough, Plasma

Performing Laboratory

Barnes-Jewish Hospital Laboratory


Quantitative Microsphere System (QMS)

Testing Algorithm:

If the gentamicin value is a critical result , #1883 Potassium, Plasma will be performed, at an additional charge. 

Literature References:

Package Insert: Gentamicin GENT by Thermo Scientific 09/2014.


Specimen Requirements

Specimen Type: Plasma

Container/Tube: 1 mint green-top (lithium heparin) tube

Specimen Volume: Full tube

Collection Instructions: Draw blood no earlier than 60 minutes prior to dose. Trough level for first dose should be drawn just prior to next dose.

Additional Information: Date and time of draw are required.

Day(s) Test Set Up

Monday through Sunday
Turnaround Time:
STAT: 1 hour after receipt in laboratory 
Routine: 2-4 hours after receipt in laboratory

Reference Values

Setting Target Range
Unspecified indication <2 mcg/mL
UTI/GPC synergy* <2 mcg/mL
Systemic illness <2 mcg/mL
Sepsis <2 mcg/mL
Physician alert value (automatic call-back)

≥2.1 mcg/mL

*UTI/GPC synergy refers to the synergistic effect of aminoglycosides with other antibiotics in treating urinary tract infections caused by gram-positive cocci (eg, Enterococcus).

Note: See Dosage Adjustment of Aminoglycoside Antibiotics Based on Drug Level Monitoring in Special Instructions.

Literature Reference:

Casabar E, BJH Antibiotic Utilization Review Subcommittee. Aminoglycoside dosing: Extended interval and traditional. BJH Pharmacy’s Toolbook (2005).

Test Classification and CPT Coding


84132-Potassium (if appropriate)

Additional Information

For BJH Laboratory Use Only
Alternate Tube:

1 dark green-top (lithium or sodium heparin) tube

1 red-top tube

1 lavender-top (EDTA) tube

Separator gel tube is acceptable but not preferred.

Analyte Stability:

Ambient:  8 hours

2° C to  8° C:  ≤48 hours

≤-20° C:  >48 hours

Laboratory Processing Instructions:

Test performed in BJH Core Lab.  Processed by automated line for delivery to the Cobas 8000. Completed specimens are stored refrigerated for 5 days.

Specimen Transport Temperature


LOINC Code Information

Name LOINC Code
Genatmicin, Trough, Plasma 3665-7