The initial steps in the pursuit to diagnose trimethylaminuria with liquid chromatography-tandem mass spectrometry and UniSpray ionization at CMMS

Sammanfattning: Trimethylaminuria is an autosomal recessive disorder characterized by a decreased oxidation capacity of trimethylamine to trimethylamine-N-oxide in the liver. The condition is diagnosed by estimating concentrations of trimethylamine and trimethylamine-N-oxide in human urine and then evaluating their respective creatinine ratios and the oxidation efficiency percentage. Values previously retrieved with liquid chromatography-tandem mass spectrometry with electrospray ionization but not the novel ionization interface UniSpray. Thus, this project aims to initiate the development of a liquid chromatography-tandem mass spectrometry diagnostic method for trimethylaminuria with UniSpray ionization. The analytes were extracted from urine with a liquid-liquid extraction method and separated with hydrophilic interaction liquid chromatography using an isocratic profile with 5 mM of ammonium formate in water and methanol and multiple reaction monitoring. Overall, the mean coefficient of variation and recovery percentage from trimethylamine spiked urine samples were lower than expected, whereas the intra-precision for trimethylamine-N-oxide was acceptable. Three urine samples had estimated oxidation percentages, but only one had derived comparable creatinine ratios to an external laboratory. Due to the inadequacy of comparative data and the precision and recovery percentage deviations, the results presented in this report need cautious interpretation. Future development of the method could include manual tuning, reconsidering the calibration curve and reference values, and comparisons to the extraction method. Although there are apparent discrepancies in the precision and reliability of the derived trimethylamine and trimethylamineN-oxide concentrations, the initial steps in the pursuit of a liquid chromatography-tandem mass spectrometry diagnostic method for trimethylaminuria provide a practical foundation to continue the development.