“…To the best of our knowledge, the LC-MS/MS assay developed and presented here is the first one published to include the biomarkers SAICAr, AICAr, beta-ureidoisobutyric acid, 2,8-dihydroxyadenine and orotidine in a single method, in addition to the previously reported panel of purines and pyrimidines. This extension is expected to facilitate the detection of the disorders ADSL [1, 3], ATIC [1, 3], UPB1 [2, 3], APRT [1, 3] and UMPS [2, 18, 19], respectively, together with the deficiencies of HGPRT [1, 3], molybdenum cofactor (MoCoD) [1, 3], thymidine phosphorylase (TP) [2, 3], dihydropyrimidine dehydrogenase (DPD) [2, 3] and dihydropyrimidinase (DHP) [2, 3]. Based on the analyte panel, the presented assay should additionally be able to detect deficiencies of adenosine deaminase (ADA) [1, 3], purine nucleoside phosphorylase (PNP) [1, 3] and xanthine dehydrogenase (XDH) [1, 3], as well as phosphoribosylpyrophosphate synthetase (PRPPS) superactivity [1, 3].…”