Abbrev Code:GENT   
Order Code:LAB28Order Name:Gentamicin Level
Methodology:Grand Itasca: Homogenous enzyme immunoassay
St Joseph: Chemiluminscent microparticle immunoassay (CMIA)
All other sites: Turbidmetric rate
CPT Codes: 80170 x1
Turnaround Time:Performed and reported 24 hours/day.
Special Instructions:Comment last dose information on request form.

Collection Instructions

Optimal Volume:2.5 mL
Minimum\Peds Volume:0.6 mL; pediatric patients only: 0.4 mL in green (lithium heparin, no gel)
Container:Red (no gel), St Joseph - Green (lithium heparin, no gel)
Alternate Containers: Green (lithium heparin, no gel), St. Joseph - Red (no gel)
Collection Instructions:Trough levels: Collect immediately prior to the next dose. Peak levels: collect 60 minutes after the end of IV infusion; 1-2 hours if decreased renal function.
Causes for Rejection:Processed >2 hours after collection and patient is receiving beta-lactam antibiotics structurally similar to gentamicin (e.g. netilmicin, sagamicin and sisomicin) or cephalosporin; collection in a gel tube

Processing and Shipping

Specimen Processing:Centrifuge and assay immediately. If testing is delayed more than 2 hours, then aliquot and freeze the sample, 1.25 mL, 0.2 mL minimum (adult) 0.1 nL minimum (peds),
Shipping Instructions:Ship on dry ice.
Stability:If specimen is received more than 2 hours after collection, check with the PCU/Clinic to see whether the patient is receiving beta-lactam antibiotics or cephalosporins; if so, cancel the test. Beta-lactam antibiotics and cephalosporins will inactivate aminoglycosides causing falsely low results.
Test Performed at or Referral Lab Chemistry  (Range, UMMC-East Bank, Lakes, Ridges, Northland, Southdale, UMMC/UMMCH-West Bank, Grand Itasca, St. Joseph's)


Critical Range:Grand Itasca: Trough: Greater than 2 ug/mL; Peak: Greater than 12 ug/mL
St Joseph: Greater than 16 mg/L
All other sites:
  • Trough: Greater than 2 mg/L; Peak: Greater than 12 mg/L
  • Greater than 16 mg/L for traditional dosing
  • Greater than 35 mg/L for single daily dosing (SDD)
Therapeutic Range:Depending on dosage:
Grand Itasca Trough 0.5-1.5 ug/mL
Grand Itasca Peak 4-8 ug/mL
Grand Itasca Random 0.5-8 ug/mL
All other sites Trough <1 mg/L; depending on dosage
All other sites Peak 5.0-12.0 mg/L; depending on dosage
Use:Monitor therapeutic dosing. Half-life is 1.5-3 h (adult <30 y); 3-6 h (adult >30 y); 4-8 h (neonate).

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