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Test Code TMP Trimethoprim, Serum

Reporting Name

Trimethoprim, S

Useful For

Monitoring trimethoprim therapy to ensure drug absorption, clearance, or compliance

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum Red


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube: Red top (gel tubes/SST are not acceptable)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Serum for a peak level should be collected at least 60 minutes after a dose.

2. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Reference Values

>2.0 mcg/mL (Peak)

Day(s) Performed

Monday, Thursday

CPT Code Information

80299

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TMP Trimethoprim, S 11005-6

 

Result ID Test Result Name Result LOINC Value
80146 Trimethoprim, S 11005-6

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

Clinical Information

Trimethoprim is coadministered with sulfamethoxazole for prophylaxis or treatment of bacterial infections. These agents are used to treat a variety of infections, including methicillin-resistant Staphylococcus aureus, and for prophylaxis in immunosuppressed patients, such as individuals who are HIV-positive.

 

Trimethoprim has a wide therapeutic index and dose-dependent toxicity. Trimethoprim accumulates in patients with kidney failure.

 

Therapeutic drug monitoring is not commonly performed unless there are concerns about adequate absorption, clearance, or compliance. Accordingly, routine drug monitoring is not indicated in all patients.

Interpretation

Most patients will display peak steady state serum concentrations of more than 2.0 mcg/mL when the specimen is collected at least 1 hour after an oral dose. Target concentrations may be higher depending on the intent of therapy.

Method Description

Samples are extracted with analyte detection by tandem mass spectrometry.(Unpublished Mayo method)

Report Available

2 to 5 days

Specimen Retention Time

14 days

Cautions

Specimens collected in serum gel tubes are not acceptable, as the drug can absorb on the gel and lead to falsely decreased concentrations.

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.