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 < 0.0001). Blood gas pH (p = 0.029), bicarbonate (p = 0.019), and aspartate aminotransferase (p = 0.005) also significantly differed between these 2 groups.


CONCLUSIONS
Referred newborns with elevated plasma C3/C2 ratios > 0.4 or ammonia levels > 200 mg/dL should be highly suspected of having MMA.
Cheng
Kang-Hsiang
KH
Department of Pediatrics, Taipei Veterans General Hospital, Taipei, Taiwan, ROC.
Liu
Mei-Ying
MY
Kao
Chuan-Hong
CH
Chen
Yann-Jang
YJ
Hsiao
Kwang-Jen
KJ
Liu
Tze-Tze
TT
Lin
Hsiang-Yu
HY
Huang
Cheng-Hung
CH
Chiang
Chuan-Chi
CC
Ho
Huey-Jane
HJ
Lin
Shuan-Pei
SP
Lee
Ni-Chung
NC
Hwu
Wuh-Liang
WL
Lin
Ju-Li
JL
Hung
Ping-Yao
PY
Niu
Dau-Ming
DM
D000108:Acetylcarnitine / Q000097:blood; D000641:Ammonia / Q000097:blood; D002331:Carnitine / Q000031:analogs & derivatives / Q000097:blood; D006801:Humans; D007231:Infant, Newborn; D008764:Methylmalonic Acid / Q000652:urine*; D015997:Neonatal Screening / Q000379:methods*; D013624:Taiwan; D053719:Tandem Mass Spectrometry / Q000379:methods*
C003223:propionylcarnitine; D000108:Acetylcarnitine; D000641:Ammonia; D008764:Methylmalonic Acid; D002331:Carnitine