Rapid screening for organic acidurias based on abnormal patterns of organic acids in neonatal urine by tandem mass spectrometry with automated flow injection

Abstract The use of tandem mass spectrometry with automated flow injection for newborn screening of organic acidurias in neonatal urine samples was demonstrated in this study. After dilution and centrifugation, urine samples were placed in an autosampler, and injected directly into a triple quadrupole instrument without chromatographic separation. According to the related diagnostic biochemical findings, 14 organic acids were selected as the specific markers for 8 organic acidurias. In order to improve the ionization efficiency, carrier flow and instrument parameters were optimized. Linearity ranged from 0.01 to 1.00 mg L-1 for methylmalonic acid/2-methyl-3-hydroxybutyric acid, isovalerylglycine, propionylglycine, 3-hydroxy-3-methylglutaric acid and 0.02 to 2.00 mg L-1 for 3-hydroxypropionic acid, methylcitric acid, n-tigloylglycine, 3-hydroxyisovaleric acid, 3-methylcrotonylglycine, glutaric acid, 3-hydroxyglutaric acid, 3-methylglutaric acid, 3-methylglutaconic acid with the linear correlation coefficients R2 all greater than 0.99. The limits of detection (LOD) of the 14 analytes were between 2.1 ∼ 7.3 μg L-1, while the limits of quantitation (LOQ) were between 5.0 ∼ 15.1 μg L-1. The relative standard deviations (RSDs) of intra-day precision and inter-day precision were in the range of 0.55–7.27% (n = 6) and 0.82–7.57% (n = 18), respectively. The recoveries of all analytes in the range of 85.49–111.64% were proved to be satisfactory. 36 positive samples of eight organic acidurias were identified effectively. The proposed method had simple and rapid analysis process, which effectively shorten the pretreatment time and successfully differentiated propionic aciduria from methylmalonic aciduria.