Newborn Screening for Methylmalonic Aciduria by Tandem Mass Spectrometry: 7 Years' Experience From Two Centers in Taiwan

Background The clinical course of methylmalonic aciduria (MMA) is fulminant in neonates and emergency management is necessary to save lives. It is therefore very important to differentiate affected from unaffected neonates immediately when there are abnormal results regarding MMA in newborn screening. Methods Between January 2002 and December 2008, 598,522 newborns were screened for MMA by 2 neonatal screening centers: the Chinese Foundation of Health and the Taipei Institute of Pathology. A total of 22 newborns were referred to confirmatory medical centers, and 7 were confirmed as having MMA. The initial propionylcarnitine (C3) level, C3/acetylcarnitine (C2) ratio, plasma ammonia, liver function tests, blood pH and bicarbonate were compared between the true-positive and false-positive groups. Results The C3/C2 ratio and plasma ammonia were markedly higher in the true-positive MMA group ( p p = 0.029), bicarbonate ( p = 0.019), and aspartate aminotransferase ( p = 0.005) also significantly differed between these 2 groups. Conclusion Referred newborns with elevated plasma C3/C2 ratios > 0.4 or ammonia levels > 200 mg/dL should be highly suspected of having MMA.