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Test Code Billings Clinic: 0228 Tacrolimus, Blood

Important Note

A trough sample is recommended for measurement of tacrolimus.

Venipuncture should occur prior to sulfasalazine and/or sulfapyridine administration due to the potential for falsely elevated results. 

Patients who have received preparations of mouse monoclonal antibodies for diagnosis or therapy should not have this assay performed. 

Patients treated with viral protease inhibitors for HIV infection may cause elevation of tacrolimus to at least 100 ng/mL and may require novel dosing. 

Performing Laboratory

Billings Clinic Laboratory:  Chemistry

Useful For

Used for the quantitative analysis of tacrolimus and metabolite in human whole blood as an aid in the management of tacrolimus therapy in liver and kidney transplant patients.

Methodology

Homogenous Enzyme Immunoassay

Specimen Requirements

  • Draw blood in a lavender-top (EDTA) tube(s).
  • Send 1 mL of unprocessed EDTA whole blood refrigerated.
  • Do not centrifuge.
  • Forward unprocessed whole blood promptly.

Storage/Stability

Specimen Type Temperature Time
EDTA Whole Blood Refrigerated 7 days
  Ambient 8 hours
  Frozen 6 months

Reject Due To

  • Specimens collected in tube other than EDTA
  • Specimens outside of the required storage requirements

Reference Values

5.0 - 15.0 ng/mL

Day(s) Test Set Up

Monday - Friday with run set up at 8 AM

Test Classification and CPT Coding

80197 - Tacrolimus

LOINC Code Information

Reporting Name LOINC Code
Tacrolimus 11253-2

Interpretive Remarks

No firm therapeutic range exists for tacrolimus in whole blood. The complexity of the clinical state, individual differences in sensitivity to immunosuppressive and nephrotoxic effects of tacrolimus, time of sample collection, coadministration of other immunosuppressants, type of transplant, time post transplant, and a number of other factors contribute to different requirements for optimal blood levels of tacrolimus. Individual tacrolimus values cannot be used as the sole indicator for making changes in treatment regimen. Each patient should be thoroughly evaluated clinically before treatment adjustments are made.