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Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
Published on: November 8, 2015
Case Report: Falsely Elevated Tacrolimus Concentrations in a Kidney Transplant Recipient
Lucas Nascimento Diniz Teixeira1, Diogo Buarque Cordeiro Cabral1, Alexandre de Holanda Cavalcanti Pinto1
1Department of Nephrology and Kidney Transplantation of the Real Hospital Português de Beneficência em Pernambuco, Pernambuco, Brazil.
Transplantation Proceedings
|July 25, 2026
Summary
False-positive tacrolimus (TAC) results from one assay led to unnecessary drug withdrawal in a kidney transplant patient. Confirmatory testing with an alternative method confirmed interference, allowing safe TAC reintroduction and appropriate immunosuppression management.
Area of Science:
- Nephrology
- Clinical Chemistry
- Immunology
Background:
- Tacrolimus (TAC) is vital for immunosuppression post-kidney transplant.
- TAC has a narrow therapeutic window, necessitating precise drug monitoring.
- Analytical interferences in TAC assays can yield inaccurate serum concentrations.
Purpose of the Study:
- To report a case of persistently elevated tacrolimus concentrations due to assay interference.
- To emphasize the importance of confirmatory testing for unexpected laboratory results.
- To highlight the clinical implications of analytical interference in immunosuppressive drug monitoring.
Main Methods:
- Case report of a kidney transplant recipient.
- Initial tacrolimus (TAC) measurement using affinity column-mediated immunoassay (ACMIA).
- Confirmatory TAC measurement using microparticle enzyme immunoassay (MEIA).
Main Results:
- ACMIA showed falsely elevated TAC levels, leading to medication suspension.
- MEIA confirmed undetectable TAC levels, indicating ACMIA interference.
- TAC was safely restarted at a lower dose, maintaining therapeutic levels.
- Patient experienced and was treated for antibody-mediated rejection, preserving graft function.
Conclusions:
- Analytical limitations of TAC assays can cause clinically misleading results.
- Unexpected TAC concentrations warrant confirmation with alternative methodologies.
- Integrating clinical judgment with laboratory data is crucial for safe immunosuppressive management and graft survival.
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