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Laboratory Medicine

Test Directory / Tacrolimus



Common AbbreviationsTAC
Tube typeEDTA
Clinical IndicationTacrolimus is an immunosuppressive drug which has shown to be effective for the treatment of organ rejection following transplantation. Tacrolimus may be administered IV or orally. Measurement is used to monitor drug levels to ensure levels remain high enough to prevent transplant rejection and low enough to prevent toxic side effects.
Specimen TypeBlood
Sample typeEDTA Whole blood
Minimum Volume1mL
Special PrecautionsNo special requirements
Stability 5 days at 15 - 25°C, 7 days at 2 - 8°C and up to 6 months at -20°C
Turnaround TimeIf received in Scarborough: Inpatient: 2 days Outpatient/ GP: 2 days If received in York: Inpatient: 24 hours Outpatient/ GP: 24 hours
Reference IntervalNo 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, co-administration of other immunosuppressants, type of transplant, time of transplant and a number of other factors contribute to different requirements for optimal blood levels.
LimitationsWhen elimination of tacrolimus is impaired (e.g. during cholestasis) tacrolimus metabolites may accumulate meaning results may be falsely elevated. Icteric samples are unsuitable for analysis. The assay is unaffected by biotin < 123 nmol/L or < 30 ng/mL and haematocrit 15 – 60%. No interference was observed from rheumatoid factors up to a concentration of 500 IU/mL. Samples should not be taken from patients receiving therapy with high biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin administration. In rare cases, interference due to extremely high titers of antibodies to analyte specific antibodies, streptavidin or ruthenium can occur. In vitro tests were performed on 16 commonly used pharmaceuticals. No interference with the assay was found. In addition, several special drugs were tested. No interference with the assay was found.
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