title: Falsely elevated whole-blood tacrolimus concentrations in a kidney-transplant patient: potential hazards.
abstract: Tacrolimus-based immunosuppression is the most frequently prescribed immunosuppression for kidney-transplant (KT) patients. Because tacrolimus has a narrow therapeutic window, drug monitoring is mandatory. Of the many methods used to assess whole-blood trough levels, antibody-conjugated magnetic immunoassay (ACMIA) is popular because, compared with microparticle enzyme-linked immunoassays (MEIA), there is no need to pretreat samples, thus reducing time taken by the laboratory technician. Herein, we report on a KT tacrolimus-treated patient who experienced falsely elevated whole-blood tacrolimus concentrations after using the ACMIA method. ACMIA gave trough levels of 24 ng/ml, whereas the actual trough level, when measured by enzyme-multiplied immunoassay technique (EMIT) and high-performance liquid chromatography coupled with mass spectrometry (LC-MS/MS), was nil. After a workup we only found one factor that might have caused the elevated concentration: positive anti-double stranded DNA autoantibodies. We conclude that, when ACMIA produces surprisingly high tacrolimus concentrations in organ-transplant patients, these should be reassessed immediately using either LC-MS/MS or another immunoassay in order to eliminate falsely elevated results.
authors.affiliation: Department of Nephrology, Dialysis and Organ Transplantation, CHU Rangueil, Toulouse, France. rostaing.l@chu-toulouse.fr
authors.forename: Lionel
authors.initials: L
authors.lastname: Rostaing
authors.forename: Olivier
authors.initials: O
authors.lastname: Cointault
authors.forename: Pierre
authors.initials: P
authors.lastname: Marquet
authors.forename: Anne-Gaelle
authors.initials: AG
authors.lastname: Josse
authors.forename: Michel
authors.initials: M
authors.lastname: Lavit
authors.forename: Franck
authors.initials: F
authors.lastname: Saint-Marcoux
authors.forename: Nassim
authors.initials: N
authors.lastname: Kamar
mesh_terms: D000974:Antibodies, Antinuclear / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D016903:Drug Monitoring / Q000379:methods*; D017248:Enzyme Multiplied Immunoassay Technique; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007166:Immunosuppressive Agents / Q000097:blood*; D016030:Kidney Transplantation / Q000276:immunology / Q000502:physiology*; D008280:Magnetics; D008875:Middle Aged; D016559:Tacrolimus / Q000097:blood*; D053719:Tandem Mass Spectrometry
chemical_list: D000974:Antibodies, Antinuclear; D007166:Immunosuppressive Agents; D016559:Tacrolimus