Reliable prenatal diagnosis of Canavan disease by measuring N-acetylaspartate in amniotic fluid using liquid chromatography tandem mass spectrometry.
OBJECTIVE
Prenatal diagnosis of Canavan disease by measuring N-acetylaspartic acid (NAA) in amniotic fluid is reliable and preferred over aspartoacylase enzyme assay especially in populations with unknown mutations. Typically based on GC-MS, existing methods are time-consuming and laborious. We developed a novel LC-MS/MS method for determination of NAA in amniotic fluid with minimal sample preparation.


METHODS
NAA and d(3)-NAA were detected by negative-ion electrospray ionization-MS/MS. Quantification was achieved by standard addition using six 0.1 mL portions of each specimen enriched with increasing NAA amounts (0, 0.05, 0.1, 0.2, 0.3, and 0.4 microg) and endogenous NAA was calculated by extrapolation.


RESULTS
Injection-to-injection time was 2 min whereas the turn around time from sample receipt was about 1 h. Intraday (n = 10) and interday (n = 10) variations were less than 9.4%. The reference range determined using gestation-matched controls (n = 12) of 1.1-2.7 micromol/L is in agreement with the literature. Specimens from at-risk pregnancies with established diagnosis (n = 4) were successfully analyzed.


CONCLUSIONS
We developed a new method that enables reliable, sensitive, and selective determination of NAA in a small volume of amniotic fluid for the prenatal diagnosis of Canavan disease. The simple sample preparation adopted in this work precluded the necessity for extraction and derivatization.
Al-Dirbashi
Osama Y
OY
National Laboratory for Newborn Screening, King Faisal Specialist Hospital and Research Centre, Riyadh 11211, Saudi Arabia. dirbashi@kfshrc.edu.sa
Kurdi
Wesam
W
Imtiaz
Faiqa
F
Ahmad
Asmahan M
AM
Al-Sayed
Moeenaldeen
M
Tulbah
Maha
M
Al-Nemer
Maha
M
Rashed
Mohamed S
MS
D000581:Amidohydrolases / Q000235:genetics; D000653:Amniotic Fluid / Q000737:chemistry*; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis; D017825:Canavan Disease / Q000175:diagnosis* / Q000209:etiology / Q000235:genetics / Q000473:pathology; D016022:Case-Control Studies; D002853:Chromatography, Liquid / Q000379:methods; D005260:Female; D005865:Gestational Age; D006801:Humans; D009154:Mutation / Q000502:physiology; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D015203:Reproducibility of Results; D012307:Risk Factors; D053719:Tandem Mass Spectrometry / Q000379:methods*
D001224:Aspartic Acid; C000179:N-acetylaspartate; D000581:Amidohydrolases; C019751:aspartoacylase