NBS in Portugal: results from a ten years experience with mass spectrometry

Marcão, Ana

http://hdl.handle.net/10400.18/2736

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Marcão, Ana

Abstract(s)

The Portuguese Neonatal Screening Program (PNSP) was established in Portugal by the Ministry of Health in the late seventies, initially for phenylketonuria (1979) and shortly after for congenital hypothyroidism (1981). Through a pilot study of 100,000 newborns, the screening of 14 inherited errors of metabolism (IEM) was initiated in 2004, by tandem mass spectrometry. In 2009, ten additional metabolic disorders were added to the screening panel, thus establishing the actual panel of 24 IEM included in the PNSP. Samples are being collected between the 3rd and 6th days of life, all over the country, and analyzed in a single laboratory, which processes around 400 daily samples. Confirmatory tests, including amino acids, organic acids and molecular analysis are also performed by the screening laboratory that works in close relation with eight specialized medical centers distribute along the country. Since 2004, a total of 820,433 neonates were screened by tandem mass spectrometry, and 345 patients were identified. Fatty acid oxidation disorders are the most common, with 134 patients diagnosed, and followed by 127 patients with amino acid disorders, 67 with organic acidemias and 17 with urea cycle defects. Individually, MCAD and disorders of phenylalanine metabolism were the most common defects. Five other IEM also presented prevalence higher than 1:100,000: glutaric aciduria type I, Cbl C deficiency, citrullinemia type I, MAT I/III deficiency and 3-methylcrotonyl CoA carboxylase deficiency. During these ten years, three infants with IEM were missed due to normal results in the screening sample. They presented clinical symptoms later in infancy and, clinical and biochemical or molecular evaluation confirmed the diagnosis of argininosuccinic aciduria, CPTII deficiency (muscular form) and Cbl D deficiency. Overall, since the use of tandem mass spectrometry, a birth prevalence of 1:2,378 was observed for IEM, and values of 18% for PPV, 99,81% for specificity and 99,42% for sensitivity were achieved.