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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Gentamicin

Test Code(s): GENT / HCGENT

CPT Code(s): 80170

Methodology: Particle Enhanced Turbidometric Inhibition Immunoassay (PETINIA)

Clinical Significance: Antibiotic

Days Performed: Daily, 24 hours.

Turnaround Time: Stat: 1 hour.
Routine: 4 hours.

Specimen Requirements

Specimen: Blood

Collection Instructions: Collect specimen for peak level 30 minutes after the end of a 30 or 60 minute infusion. Collect specimen for trough level 15 - 30 minutes prior to start of infusion.

Collection Container: Preferred: Red top
Also Acceptable: Green top (with lithium heparin anticoagulant)

Collection Volume: Preferred: 2 mL
Pediatrics: 0.4 mL

Sample Analyzed: Serum or plasma

Volume Required: Preferred: 1 mL
Pediatrics: 0.2 mL

Specimen Processing: Centrifuge immediately.  Transfer cell-free serum or plasma to plastic vial.  Refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220) within 60 minutes of collection if on ice. Transport within 30  minutes if not on ice.  Transport frozen serum on dry ice if coming from outreach location.

Unacceptable Criteria: Specimens collected in red cap with yellow ring (SST) or green cap with yellow ring (PST) tubes are not acceptable.
Specimens greater than 2 hours old, uncentrifuged when received by the laboratory, are not acceptable.

Stability: Ambient: 2 hours unspun; 8 hours spun
Refrigerated: 3 days
Frozen: 1 month


 Optimal therapeutic ranges:  


 4-10 mcg/mL


 < 2 mcg/mL


Test Limitations:

Aminoglycosides structurally similar to gentamicin (e.g. Sisomycin, Sagamicin and Netilmicin) may significantly cross-react with this method. Therefore, gentamicin cannot reliably be used for patients receiving these antibiotics separately or in combination with gentamicin.

Critical Calls: View

Additional Information:

Result of "BELOW" indicates that the result is below the method detection limit of 0.2 mcg/mL. Gentamicin is an aminoglycoside antibiotic which exhibits high potency and broad spectrum antibacterial action against both gram-negative and gram-positive organisms. Patient samples which contain the drugs Sisomycin and Netilomycin will yield falsely elevated values for Gentamicin.

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