title: False tacrolimus concentrations measured by antibody-conjugated magnetic immunoassay in liver transplant patient: 2 case reports and literature review.
abstract: 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.
authors.affiliation: Department of Pharmacy, Kumamoto University Hospital, Kumamoto, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Taguchi
authors.forename: Takafumi
authors.initials: T
authors.lastname: Ohmura
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ohya
authors.forename: Momoko
authors.initials: M
authors.lastname: Horio
authors.forename: Kumiko
authors.initials: K
authors.lastname: Furukawa
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Jono
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Inomata
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Saito
mesh_terms: D000368:Aged; D016903:Drug Monitoring / Q000379:methods*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000097:blood*; D016031:Liver Transplantation; D008280:Magnetics / Q000379:methods*; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D016559:Tacrolimus / Q000008:administration & dosage / Q000097:blood*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D007166:Immunosuppressive Agents; D016559:Tacrolimus