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Test Code Billings Clinic: 4353 Gentamicin, Trough, Plasma or Serum

Important Note

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

Performing Laboratory

Billings Clinic Laboratory: Chemistry

Useful For

Monitoring adequacy of drug clearance during gentamicin therapy

Methodology

PETINIA / Turbidimetric Rate

Specimen Requirements

Submit only 1 of the following specimens:

Serum or plasma should be physically separated from cells as soon as possible with a maximum limit of two hours from the time of collection.

  • Plasma or serum for a trough level is usually drawn just prior to next dose.

  • Date and time of last dose are required on request form for processing.

  • Indicate plasma or serum on request form.

  • Label specimen appropriately (plasma or serum).

 

Plasma

  • Draw blood in a green-top (lithium heparin) tube(s).
  • Spin down and send 1 mL of heparinized plasma frozen in plastic vial.

Serum

  • Draw blood in a plain, red-top tube(s).
  • Spin down and send 1 mL of serum frozen in plastic vial.

Storage/Stability

Specimen Type Temperature Time
Plasma, Serum Refrigerated 2 days
  Frozen (preferred) 1 month
  Ambient 8 hours

 

Reference Values

Therapeutic concentration:                      0.0 - 0.9 µg/mL
Call-back toxic concentration value:       ≥ 1.0 µg/mL

Day(s) Test Set Up

Daily

Test Classification and CPT Coding

80170 - Gentamicin

LOINC Code Information

Reporting Name LOINC Code
Gentamicin Trough 3665-7
Gent Tr Dose and Time 45285-4