Test Code TOBT Tobramycin Level, Trough
Additional Codes
| EPIC | LAB5327 |
Synonyms
- Tobrex
- Nebcin
- Bethkis
Clinical Significance
Tobramycin is an aminoglycoside antibiotic used in the treatment of infections caused by Pseudomonas aeruginosa, Proteus species, E. coli, Klebsiella, Serratia, Citrobacter, Staphylococcus aureus, Enterobacter and other microorganisms.
Tobramycin’s toxic effect is produced by interfering with ribosomal protein synthesis. Tobramycin undergoes very little, if any, metabolization and is, therefore, eliminated as the parent drug by glomerular filtration. The half‑life of tobramycin in serum or plasma correlates closely with renal function and thus is quite variable between individuals and within one individual over time. Serum or plasma tobramycin concentration is also impacted by mode of administration, the volume of extracellular fluid, the duration of the treatment and physiological changes during the illness and therapy. The therapeutic range of tobramycin should be measured at peak as well as trough concentrations. In patients with pre‑existing renal damage or those to whom tobramycin has been administered for prolonged periods or in doses above the therapeutic range, hearing impairment and/or nephrotoxicity may develop. Therefore, monitoring of peak and trough tobramycin serum or plasma levels is critical in the prevention of these serious complications with the adjustment of dosage administration as indicated.
Source: Roche Cobas TOBR2 Method Sheet Version 4.0 2024-07
Methodology
Homogeneous enzyme immunoassay (Roche Cobas c503)
Sample Type
| Preferred Sample Type | |
|---|---|
| Light green top - Plasma | |
| Acceptable Sample Type(s) | |
|---|---|
| Dark green top - Plasma | |
| Yellow top - Serum | |
| Red top - Serum | |
Centrifuge: Yes
Specimen Minimum Volume
55 uL with insert cup
Specimen Stability
| Temperature | Time |
|---|---|
| Ambient (18-25°C) | N/A |
| Refrigerated (4-8°C) (store) | 3 days |
| Frozen (-15 to -20°C) | 1 month* |
Separate plasma or serum from cells within 2 hours.
NOTE: Stability limits only valid for capped specimens.
*Freeze only once!
Reference Ranges
| Therapeutic Range |
|---|
| 0.5 - 2.0 ug/mL |
| Critical Values |
|---|
| >2.0 ug/mL |
| Technical Range |
|---|
| 0.4 - 10.0 ug/mL |
Rejection Criteria
| Hemolysis | Index >800 |
|---|---|
| Icterus | Index >30 |
| Lipemia | Index >750, ultracentrifuge |
Availability
| Performed | STAT |
|---|---|
| 24/7 | Yes |
Performing Laboratory
MultiCare Yakima Memorial Hospital Laboratory
Lab Department
Chemistry
CPT Code
80200
LOINC
4059-2 Tobramycin trough [Mass/Vol]