Newborn screening with tandem mass spectrometry: 12 months' experience in NSW Australia

Since 1998, the NSW Newborn Screening Program has used electrospray tandem mass spectrometry (MS/MS) to analyse samples from all babies born in NSW an d the ACT (approximately 95 000 per year) for selected amino acids and acyl carnitines. The software rules editor initially interprets all results wher e ratio of analyte to internal standard is modified by input from the exter nal standard curves per analyte, The numerical results are then downloaded to the NSW Newborn Screening database. which provides automatic, analyte sp ecific follow-up test cascade. We have analysed samples from 137 120 consec utive newborns received by the program, requested repeat samples from 122 b abies, and found abnormal levels in 17 babies with phenylketonuria, 1 tetra hydrobiopterin deficiency, 3 hyperphenylalaninaemia, 1 maple syrup urine di sease, 1 tyrosinaemia type II, congenital lactic acidosis, 2 medium-chain a cyl CoA dehydrogenase deficiency, 1 short-chain acyl CoA dehydrogenase defi ciency, 1 beta-ketothiolase deficiency, 2 vitamin B12 deficient babies of v egan mothers and 1 glutaric aciduria type I. Using population data plus tha t obtained from retrospective samples with proven disorders we have establi shed cutoff levels for each analyte tested. This coupled with the ability o f the database to provide ratios of various analytes gives excellent screen ing specificity and sensitivity for the detection of at least 40 rare inbor n errors of metabolism.