Screening blood spots for argininosuccinase deficiency by electrospray tandem mass spectrometry.

Argininosuccinase deficiency is relatively more common in Saudi Arabia than other urea cycle detects (UCD) and its presentation is usually acute and virtually identical to the clinical presentation of other UCD. We developed a rapid, sensitive, and specific screening method for the diagnosis of argininosuccinase deficiency from blood spots. using electrospray tandem mass spectrometry. A 96-well microplate batch process is used for extraction of argininosuccinic acid (ASA), other amino acids and acylcarnitines (Rashed et al. 1995). ASA and other metabolites are derivatized to the corresponding butyl derivatives. The tris-butyl ester of ASA (MH = 459.3) yields two major fragments at m/z 70 and m/z 144 under mild collision induced collision. montitored in the product ion spectrum using a narrow mass range (65-150 kDa). A processing algorithm "CAMPA" is used to automatically calculate the height ratios of selected masses and flags data files as "abnormal" when certain threshold is exceeded. The method is integrated with our existing 2-minute MS/MS method for profiling amino acids and acylcarnitines (Rashed et al. 1997). Using this approach for two years we diagnosed 16 ALD cases from 14 hyperammonemic infants, one high-risk newborn, and one from a regular newborn screening blood spot.

The diagnosis and management of MSUD in Saudi Arabia by using two different methods.

Plasma amino acid concentrations were measured in Maple Syrup Urine Disease (MSUD) infants using reversed phase high performance liquid chromatography (HPLC). The technique involved an automated data acquisition system and phenylisothiocyanate (PITC) pre-column derivatization. During a period of three years more than 14 cases of MSUD have been confirmed in our hospital suggesting an alarmingly high rate of incidence of this disease in the Kingdom as compared to the West. We present here a simple and reliable method of quantitating the branched chain and other amino acid concentrations in plasma samples of children with metabolic disorders. In addition, we also present a fluorimetric COBAS based enzymatic method for the rapid semiquantitative measurement of branched chain amino acids for a disease in which a prompt initial diagnosis is essential.