False tacrolimus concentrations measured by antibody-conjugated magnetic immunoassay in liver transplant patient: 2 case reports and literature review

Kazuaki Taguchi, Takafumi Ohmura, Yuki Ohya, Momoko Horio, Kumiko Furukawa, Hirofumi Jono, Yukihiro Inomata, Hideyuki Saito

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Safe use of tacrolimus relies on regular whole-blood drug monitoring. Of the methods used to assess whole-blood tacrolimus concentration, antibody-conjugated magnetic immunoassay is mostly used for therapeutic drug monitoring because it requires only a minimal sample preparation and no pretreatment procedure. However, several cases recently have been reported in which abnormally false elevated tacrolimus concentrations were measured by antibody-conjugated magnetic immunoassay (>15 ng/mL), despite the absence of clinical symptoms. We present 2 cases of falsely detected tacrolimus concentrations that did not show abnormally high values within the therapeutic range. Whole-blood tacrolimus concentrations obtained by antibody-conjugated magnetic immunoassay showed well-controlled concentrations (approximately 2-8 ng/mL), whereas those obtained by another immunoassay and in washed erythrocytes were below the assay range (< 1.2 ng/mL). Thus, antibody-conjugated magnetic immunoassay can elicit falsely positive results of tacrolimus concentrations, even though they are within the therapeutic range.

Original languageEnglish
Pages (from-to)474-478
Number of pages5
JournalExperimental and Clinical Transplantation
Issue number5
Publication statusPublished - 2014 Oct 1



  • Liver transplant
  • Outcome

ASJC Scopus subject areas

  • Transplantation

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