Newborn Screening Program In The Community Of Madrid: Evaluation Of Positive Cases

Background: Tandem mass spectrometry (MS/MS) is being used for newborn screening since this laboratory testing technology increases the number of metabolic disorders that can be detected from dried blood-spot specimens. In the Community of Madrid, it was implemented in March 2011 and it includes 13 aminoaciaopathies, fatty . acid oxidation disorders and organic acidemias. The aim of this study was to describe our experience and evaluate the screening positive cases in a period of 9 years (2011-2019).Methods: During the period of the study, a total of 592.822 neonates were screened with this expanded program by MS/MS in the Community of Madrid. Amino acids, acylcarnitines, and succinvlicetone were quantified in all samples that met the quality criteria. Means. medians, percentiles and standard deviation of the analytes and ratios of interest were calculated.Results: 901 patients (0,15 %) with a positive screening test were referred to clinical evaluation. 230 patients were diagnosed of 30 different inborn errors of metabolism (prevalence 1:2577), 11 of which were not included as a target in the Community of Madrid newborn screening program. The global positive predictive value was 25,6 %. During this period of time, two false negative cases were detected. "The most prevalent disorders were phenylketonuria/hyperphenylalanineinia and medium chain acyl-CoA dehydrogenase deficiency (1:6444 and 1:13174 respectively). 93 % of the patients were detected in the presymptomatic stage.Conclusions: During the last 9 years a large number of cases of IEM have been detected with an acceptable global positive . predictive value. These results confirm the utility of inborn errors of metabolism newborn screening as a public health program.