Pilot study of expanded newborn screening for 573 genes related to severe diseases in China: results from 1173 newborns

Abstract

Background: Current newborn screening (NBS) in China is mainly aimed at detecting biochemical levels of metabolites in the blood, which may generate false positive/negative results. To explore whether next-generation sequencing (NGS) for dried blood spots can increase the detecting rate of genetic disorders, we carried out a pilot study using NGS in 1,173 newborns who had been tested by traditional NBS. With a focus on inherited metabolic diseases (IMDs), our team investigated the current frequencies of genes related to common inherited metabolic diseases in this cohort. Methods: We designed an NGS panel of 573 genes related to severe diseases and performed NBS in 1,173 individuals who had been screened by tandem mass spectrometry (MS/MS) as well as for phenylalanine (Phe), thyroid-stimulating hormone (TSH), 17-α-hydroxyprogesterone (17-OHP), and glucose-6-phosphate dehydrogenase (G6PD) abnormalities in a traditional biochemical NBS conducted in September 2016. We compared the biochemical results to the genetic variants and investigated the carrier frequencies of 77 genes related to disorders by MS/MS in these newborns.Results: The biochemical results showed that four newborns (all male) were positive for G6PD by enzymatic assay, while the other biochemical findings including MS/MS, Phe, TSH and 17-OHP were negative. Genetic analysis results revealed that all the four newborns with positive G6PD values harbored hemizygous G6PD mutations. The NGS results also revealed an individual (ID 84123) carrying two SLC22A5 mutations (c.760C>T/p.R254* and c.1400C>G/p.S467C) common in Chinese patients with carnitine deficiency, which were later verified to be in trans, who was biochemically negative in 2016. The MS/MS results in 2019 showed free carnitine deficiency, consistent with the genetic analysis findings. The top five genes with the highest carrier frequencies in these newborns were PAH (1.77%), ETFDH (1.24%), MMACHC (1.15%), SLC25A13 (0.98%), and GCDH (0.80%). Conclusions: Our study provided data combing biochemical results with genetic variants in 1,173 newborns and confirmed a primary carnitine deficiency patient with false-negative biochemical results. This is also the first study to report the carrier frequencies of 77 IMD-causing genes in China.