Evaluation of a Nanoparticle-Based Busulfan Immunoassay for Rapid Analysis on Routine Clinical Analyzers

Busulfan is an alkylating agent used in allogeneic hematopoietic stem cell transplantation for various malignant and nonmalignant disorders. Therapeutic drug monitoring of busulfan is common because busulfan exposure has been linked to veno-occlusive disease, disease relapse, and failed engraftment. The authors developed an automated immunoassay, along with stable calibrators and controls, and quantified busulfan in sodium heparin plasma. METHODS: The authors evaluated a homogenous nanoparticle immunoassay, the MyCare Oncology Busulfan Assay Kit (Saladax Biomedical, Inc), for precision, sensitivity, accuracy, and linearity on an open channel clinical chemistry analyzer; they compared the method with 2 mass spectrometry methods (liquid chromatography–tandem mass spectrometry and gas chromatography/mass spectrometry), using anonymized, remnant patient samples. RESULTS: The coefficients of variation for repeatability and within-laboratory precision were ≤9.0%. The linear range was 150–2000 ng/mL; samples up to 6000 ng/mL can be measured with sample dilution. Measured values deviated by ≤14% from assigned values. Comparison between validated mass spectrometry methods resulted in a correlation coefficient R ≥ 0.995. CONCLUSIONS: The MyCare Busulfan Assay Kit shows the precision, accuracy, linearity, and test range for performing busulfan concentration measurements in sodium heparin plasma on routine clinical chemistry analyzers.