Mass spectrometry assay method for detection and quantitation of kidney function metabolites

A method for detecting and determining in a sample the amount of five or more kidney function analytes, the method comprising:

• a) purifying the sample by liquid chromatography;
• b) subjecting the purified sample to an ionization source under conditions suitable to produce one or more ions detectable by mass spectrometry from each of the five or more of the analytes selected from the group consisting of N-acetylthreonine, TMAP, phenylacetylglutamine, tryptophan, creatinine, N-acetylalanine, 3-methylhistidine, trans-4-hydroxyproline, kynurenine, urea, and pseudouridine, wherein the analytes are not derivatized prior to ionization;
• c) measuring, by tandem mass spectrometry operated in positive mode in a single injection, the amount of the one or more ions from each of the five or more analytes, wherein the one or more ions used to determine the amount of each of the five or more analytes is one or more ions selected from the ions in Tables 3 and 5;
• wherein an eluent from the liquid chromatography step is directly and automatically introduced into an electrospray source of the mass spectrometer;
• and
• d) using the measured amount of the one or more ions to determine the amount of each of the five or more analytes in the sample.