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

Taguchi K, Ohmura T, Ohya Y, Horio M, Furukawa K, Jono H, Inomata Y, Saito H
Exp Clin Transplant. 2014 12 (5): 474-8

PMID: 24206050 · DOI:10.6002/ect.2013.0113

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.

MeSH Terms (15)

Aged Drug Monitoring False Positive Reactions Female Humans Immunoassay Immunosuppressive Agents Liver Transplantation Magnetics Middle Aged Predictive Value of Tests Reproducibility of Results Tacrolimus Time Factors Treatment Outcome

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