A unified liquid chromatography–mass spectrometry (LC-MS) method for quantitation of biomarkers of inherited metabolic disorders associated with urolithiasis
Huub W A H Waterval, Ping Wang, Ann Goossens, Ardy G C Beurskens, Oakley J Oppenhausen, Mark J C M van Dam, Marek J Noga, Irene M L W Körver-Keularts, Daphna D J Habets, Laura K M SteinbuschAbstract
Background and Aims
Inborn metabolic diseases (IMD) are important causes of urolithiasis in paediatric and adult patients. Especially when stones arise at a young age the screening for IMD related biomarkers is warranted. The diagnostic reports often over-report by not only giving results on the specific metabolites important for stone formation, but also on all other metabolites quantified in those assays. We aimed at developing and implementing a simplified quantitative method to consolidate three assays in one targeted LC-MS urolithiasis screening. In this screening method we included nine key metabolites involved in purine, pyrimidine, glyoxylate, and amino acid metabolism. This method consolidates three classical assays (amino acids quantification, purine & pyrimidine quantification and organic acids analysis) into one simplified workflow.
Methods
analysis of nine metabolites, and their individual internal standards, in urine was achieved with a run-to-run time of 35 minutes by LC- MS.
Results
We successfully validated this new method with a good correlation with the previously used three separate assays. Urine pH did hardly affect metabolite quantification. Age-dependent reference ranges were established and patient samples from persons with a confirmed IMD were all correctly identified in the clinical validation.
Conclusions
This streamlined assay supports improved implementation of urinary metabolic screening in urolithiasis workups.