Expanding the screening of newborns for detecting inborn errors in metabolism using next generation sequencing following mass spectrometry/immunoassay

Abstract

Inborn errors of metabolism are rare inherited disorders which leads to significant morbidity and mortality in patients. Very few studies have been conducted in India to assess prevalence of Inborn Errors of Metabolism (IEM) in newborns. We proposed testing by TMS/TR-FIA followed by NGS. This pilot study would be one of the first expanded NBS studies in India.The aim of this study was to determine the prevalence of IEM in newborns based on the samples received at Metropolis Global Reference Lab, India. Next-generation sequencing (NGS) was done as a confirmational analysis for patients tested presumptive positive on Newborn screening using Tandem Mass spectrometry (TMS) and Time-resolved fluoroimmunoassay (TR-FIA).  Two years retrospective study was conducted based on incidences of IEM using TMS and TR-FIA. NGS testing was performed on presumptive positive newborns for cystic fibrosis (CF), galactosemia and urea cycle disorder/ organic academia (UCD /OA) who had undergone NBS by TMS and TR-FIA. Highestprevalence of 1.98% & 1.58% was detected for G6PD and TSH respectively by TR-FIA. Prevalence of AA disorders (3.20%), OA (1.60%) and UCD (1.43%) was observed to be the highest amongst the diseases detected by TMS. Presumptive positive case of Argininemia and Cystic Fibrosis were found to be concordant with NGS. Out of three presumptive positive cases, one presumptive positive case of CF and two of galactose were found discordant.   Our prevalence study showed similarities to the prevalence reports published by other Asian countries. Expanded NBS program can be improved by including NGS as a first follow-up test after detection of abnormal metabolites in DBS. This approach will help in reducing the encumbrance of false-positive as well as false-negative cases. Our study will be influential in conducting more prospective studies and routine implementation of NGS-based analysis in NBS in India.