Ultra-Fast Measurement of Metformin in the Clinical Setting Using Probe Elecrospray Ionization Mass Spectrometry (PESI-MS).
Résumé
Metformin is a treatment used for type 2 diabetes. Lactic acidosis (LA) is a frequent complication that can either be induced by or associated with elevated metformin plasma concentrations. When coupled with a mass spectrometry system (MS), the Probe Electrospray Ionization (PESI) method allows direct and rapid analysis of different types of matrices without pre-treatment. In this study we developed a PESI-MS method for the determination of metformin in plasma. We used a tandem mass spectrometer equipped with a PESI source in the reaction monitoring mode for the quantitation of metformin. Metformin-D6 was chosen as internal standard, following an isotope dilution approach. The method was fully validated with 6 concentration levels (0.5 to 50 mg/L). The matrix effect was evaluated for each level and the specificity was tested with a mix of potential co-medications. Using patient samples, the performance was compared with 2 classical LC-MS/MS and LC-DAD methods used in external labs. Sample preparation consisted in mixing 10\textmu L plasma in 1000\textmu L ethanol/ ammonium formate buffer including metformin-D6 at a fixed concentration of 5 mg/L. Total run time was 0.31 min. Isotope dilution gave satisfactory results of accuracy and precision (min-max: -12.1-15.8% and 1.0-17.1%, respectively). The matrix effect was fully corrected by the internal standard (bias < 1%). The specificity study also reported satisfactory results. Finally, in a representative group of 29 patients (55% with a concentration <5 mg/L, 38% with a concentration >5 mg/L and 7% not detected), we observed almost identical results when comparing LC-DAD and LC-MS/MS to PESI-MS (r2 > 0.99).We propose a specific, sensitive, accurate and ultra-fast solution for the measurement of metformin in patient plasma, with no sample preparation or calibration curve building. This could be helpful in a core Lab when rapid diagnosis of lactic acidosis is needed.