Puzzling interference in the Siemens tacrolimus assay in a renal transplant patient: A case report.

Background: Therapeutic drug monitoring is a key tool for optimizing tacrolimus therapy in transplant recipients. The modified ACMIA assay from Siemens Healthcare Diagnostics is an immunoassay commonly used for tacrolimus monitoring, but it is not known whether this assay is resistant to interference from endogenous substances in real-world use.

Objective: To describe a case of unexpected interference in tacrolimus monitoring using the modified ACMIA method in a kidney transplant recipient, and to highlight the importance of careful interpretation of laboratory results and effective communication with clinicians in optimizing patient care.