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Gentamicin Level, Serum

Gent

Test Codes

LEVEL: EPIC: LAB5392, Beaker: GENTA, Antrim: 17510,  PEAK: EPIC: LAB5393, Beaker: GENTP, Antrim: 17248,  TROUGH: EPIC: LAB5394, Beaker: GENTT, Antrim: 17500,  EID: (Is ONLY performed at Grosse Pointe, Royal Oak and Troy) EPIC: LAB5395, Beaker: GENTD, Antrim: 17500

Department

Chemistry

Specimen Collection Criteria

Collect: One plain Red-top tube. (Minimum Whole Blood: 1.0 mL)

Do not use Serum Separator Tubes.
See Minimum Pediatric Specimen Requirements for Microtainer^® collection.
Time of Collection: Consult Pharmacy Dosing Service.
A common sampling time for peak measurement is 30 minutes after cessation of an IV infusion.
A common sampling time for trough measurement is just prior to the next dosage administration.
Record the exact time of specimen collection on the tube or in the computer system.

Physician Office/Draw Specimen Preparation

Let specimens clot 30-60 minutes and refrigerate (2-8°C or 36-46°F) within two hours of collection. (Minimum: 1.0 mL blood)

Preparation for Courier Transport

Transport: Collection tube, refrigerated (2-8°C or 36-46°F). (Minimum: 1.0 mL blood)

Rejection Criteria

• Serum Separator (SST) tubes.
• Severely lipemic or hemolyzed specimens. 

In-Lab Processing

Let specimens clot 30-60 minutes and centrifuge to separate serum from cells. Deliver an aliqout of serum or the collection tube immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Collection Tubes
Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Dearborn Chemistry Laboratory
Royal Oak Chemistry Laboratory

Performed

Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 24 hours.

Reference Range

Conventional Dosing
Peak: 5-10 mcg/mL. (Critical: Greater than 12 mcg/mL.)
Trough: Greater than 2 mcg/mL. (Critical: Greater than 2.5 mcg/mL.)

Once-A-Day Dosing
Greater than or equal to 20 mcg/mL. (Critical: Greater than 20 mcg/mL.)

Test Methodology

Particle Enhanced Turbidimetric Inhibition Immunoassay.

Interpretation

Once-a-day aminoglycoside therapy will produce peak levels higher than critical values but not necessarily damaging to the kidneys. Individuals with impaired renal function will probably require a decrease in dose or an increase in their dosing interval. Patients' samples which contain the drugs sagamicin, sisomycin, and netilmicin can falsely elevate gentamicin levels. These drugs are not commonly co-administered with gentamicin.

High concentration of penicillins or cephalosporins have been shown to inactivate gentamicin in vitro.

Samples from patients receiving additional antibiotics of these types should be assayed immediately or stored frozen.

Clinical Utility

Gentamicin is an aminoglycoside antibiotic which exhibits high potency and a broad-spectrum bacterial action primarily against gram-negative organisms. Gentamicin is associated with renal and ototoxicity upon extended use. Therapeutic monitoring is advantageous particularly in patients with diminished renal function.

CPT Codes

80170

Contacts

Last Updated

10/25/2023