Tacrolimus is an
immunosuppressive agent used to prevent post-
transplantation rejection.
Tacrolimus has a narrow
therapeutic window and therefore, its whole
blood concentration is measured for
therapeutic drug monitoring. In this
report, we present two cases of falsely elevated
tacrolimus concentrations identified in recipients of solid
organ transplants due to analytical interferences in the antibody-conjugated
magnetic immunoassay (ACMIA)
method used.
Tacrolimus concentrations measured using ACMIA were 4- to 8-fold higher than the values obtained using liquid-
chromatography-
tandem mass spectrometry (
LC-MS/MS) or chemiluminescent micro-particle
immunoassay. The cause of this interference remains unknown, but the identification of a possible false elevation of
tacrolimus is of paramount importance in clinical practice. Pre-
treatment of samples by
ethanol extraction or using alternative
methods of
tacrolimus measurement such as
LC-MS/MS are necessary to obtain reliable results in the event of an analytical interference.