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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

Internal Resources


Item Value
Available Stat? Yes
Test code GENA
Performed by? Chemistry
Sendout? no
Price range $$$
In House Availability Routine: 7 days; STAT: 24 hours/ 7 days
Principle The Siemens Centaur assay is a competitive immunoassay using direct chemiluminescent technology.
Container type gold top gel tube
Amount to Collect 2 mL
Collection Instructions Plasma samples cannot be assayed.
Sample type Blood
Special instructions Peak serum levels should be drawn one hour after infusion is finished (infusion usually takes one hour). Trough serum level should be drawn 30 minutes before the next dose.
Normal range
Peak: 5.0 – 10.0 mg/L 10.5-20.9 mcmol/L
Trough: 1.0 – 2.0 mg/L 2.1-4.2 mcmol/L

Values > 12.0 mg/L (> 25.1 mcmol/L) are considered Critical Values and are called to the physician or patient care unit immediately.
Stability 6 hrs at RT or 4°C if penicillin (and/or other beta-lactam antibiotics) are co-administered; otherwise, 48 hrs at 4°C; 1 month at -20°C.
Interferences 1. High concentrations of β-Lactam antibiotics (penicillins and cephalosporins) inactivate gentamicin in vivo and in vitro.

2. Auto- (rheumatoid factor) and heterophile antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays. Patients routinely exposed to animals or to animal serum products can be prone to this interference. Anomalous values, spuriously low or high, may be observed. Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).
Additional information Trough levels correlate with renal toxicity. Peak levels correlate with therapeutic efficacy. Patients with renal failure accumulate drug, requiring dose reduction or longer dose intervals. These patients should have an ID-Pharmacology consult to determine optimal dosing and monitoring schedules.
References 1. Bayer 125827 Rev. A, 9/2000. Siemens Medical Solutions Diagnostics, Malvern, PA.

2. Kallmetu, G. Gentamicin and Tobramycin: Clinical Pharmacokinetics and nephrotoxicity. Aspects of assay techniques. Scan J. Infect Div Suppl. 18:1, 1979.

3. Young, DS. Effects of Drugs on Clinical Laboratory Tests, 4th ed. Washington DC: AACC Press; 1995.
CPT coding 80170
Last Updated 10/24/2012 11:28:32 AM
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