Validated LC-MS/MS reference method enables global standardization of meropenem therapeutic drug monitoring

Original abstract

OBJECTIVES: Therapeutic drug monitoring (TDM) of meropenem is critical for optimizing clinical efficacy and minimizing toxicity. We describe the validation of an isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) candidate reference measurement procedure (RMP) for the quantification of meropenem in human serum and plasma. METHODS: A high-purity meropenem standard was characterized using an in-house quantitative nuclear magnetic resonance protocol. This established the absolute content and ensured an unbroken chain of metrological traceability to the International System of Units. Samples were prepared via incubation with a stable isotope-labeled internal standard followed by protein precipitation. Analysis was performed using LC-MS/MS with electrospray ionization. The method was validated to assess selectivity, matrix effects, precision, accuracy, and measurement uncertainty according to international metrological guidelines. RESULTS: The candidate RMP demonstrated high selectivity across a linear range of 0.400-120 μg/mL and was unaffected by matrix interferences. Intermediate precision was <3.8 % for spiked serum and <4.3 % for native patient pools; repeatability ranged from 1.9 to 3.1 %. Mean bias ranged from -5.1 to 2.4 % across all serum and plasma levels, including dilution integrity assessments. Expanded measurement uncertainty (k=2) for target value assignment (n=6) was 2.6-4.3 %, while uncertainty for single measurements ranged from 6.0 to 8.8 %. CONCLUSIONS: The proposed method fulfills all analytical performance specifications required for a candidate RMP. By establishing a direct link from individual patient samples to primary reference materials, this approach provides a robust foundation for the global standardization of routine meropenem assays.