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Lab Manual for UCSF Clinical Laboratories

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Item Value
Test Update Information Effective April 19, 2016, tobramycin testing is now being performed on the Beckman DxC 800 instrument. Results run approximately 10% higher on this platform.
Approval req'd? No
Available Stat? No
Test code TOBPK (Peak), TOBTH (Trough), TOBRN (Random)
Performed by Parnassus Chemistry
In House Availability 24 hours per day and 7 days per week
Method Particle enhanced turbidimetric inhibition immunoassay (Beckman DxC 800)
Collection Instructions Time to Steady State: 2-3 doses (1 dose for ICN extended interval dosing).

Collect trough samples 30 minutes prior to 3rd or 4th dose.

For patients on hemodialysis collect just prior to and/or 1 hour post dialysis

For standard dosing draw peak samples 30 minutes after the end of infusion. For ICN extended interval dosing draw peak 30 minutes after end of 4th dose

Note the exact time of collection on BOTH the sample and in Apex (or on any paper orders).

Bring to lab immediately for processing if patient also receiving carbenicillin or other high dose penicillin or cephalosporin because prolonged interactions with these drugs (8 hours or more) at room temperature can modify amino groups and interfere with aminoglycoside assay.
Container type Gold top or Light Green top
Amount to Collect 1 mL blood
Sample type Serum or plasma
Preferred volume 0.5 mL serum or plasma
Min. Volume 0.2 mL serum or plasma
UCSF Rejection Criteria Collection time not indicated on sample
Processing notes Mission Bay and Mount Zion: Refrigerate serum or plasma and send to Parnassus Chemistry
Units mg/L
Normal range
Therapeutic peak 5-10 mg/L

Trough levels:
Standard dosing < 2 mg/L (< 1 mg/L optimum)
Once daily, high dose < 1 mg/L (< 0.3 mg/L optimum)
ICN extended interval dosing < 2 mg/L (< 1.5 mg/L optimum)
CF extended interval dosing < 1 mg/L

Source of reference range: UCSF/SFGH/VASF joint guidelines for antimicrobial use in adults.

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Stability Separate serum or plasma from cells within 2 hours of collection
Separated serum or plasma is stable at room temperature for 8 hours.
Refrigerated samples are stable 48 hours
Turn around times 1 day
Additional information For desired peak and trough levels in special situations, Click here

Toxicity associated with trough levels > 2 mg/L or peak levels > 10-12 mg/L

Click here for: A Guide on Drug Level Monitoring
CPT coding 80200
LOINC code 35670-9
Last Updated 4/21/2016 5:19:46 PM
Entry Number 928
Lab Procedure Link Click here for procedure
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