Determination of Trimethylamine-N-oxide by a Simple Isocratic High-Throughput Liquid-Chromatography Tandem Mass-Spectrometry Method.

Background: As trimethylamine-N-oxide (TMAO) is considered to be associated with various diseases, rapid determination of serum TMAO concentration is of clinical interest. This study is aimed at evaluating the analytical performance of a simple isocratic liquid chromatography-tandem mass-spectrometry (LC-MS/MS) method for TMAO quantification.

Methods: TMAO measurements were performed on a tandem mass spectrometer, SCIEX QTRAP 4500 (Applied Biosystems, Framingham, MA, USA), coupled with an Agilent 1260 Infinity HPLC system (Agilent Technologies, Santa Clara, CA, USA). The separation was performed on a Hypercarb Porus Grahitic Carbon (PGC) column (ThermoFisher Scientific, Waltham, MA, USA) by isocratic elution mode. Linearity, precision, recovery, and pre-analytical requirements of the TMAO LC-MS/MS method were evaluated. The imprecision acceptance criteria were defined 15%. We investigated sample stability at room temperature (RT) and assessed the serum TMAO concentrations of 188 healthy adults.

Results: The TMAO LC-MS/MS method was linear over the concentration range of 0.5 - 80 μmol/L. Intra- and inter-day precision ranged between 2.24 - 3.37% and 6.95 - 9.97%, recovery between 106 - 114%, respectively. At RT, serum samples were stable for 8 days. The median serum TMAO concentration of 188 healthy adults was 2.27 μmol/L (2.5th and 97.5th percentile: 0.75 - 10.46 μmol/L), respectively.

Conclusions: The isocratic TMAO LC-MS/MS shows a broad analytical range and meets the imprecision acceptance criteria of 15%. This method is a robust and reliable diagnostic tool for the assessment of the human TMAO status. Serum samples are stable at RT for at least 8 days.