Increased primary carnitine deficiency detection through second-tier newborn genetic screening
Abstract Background Newborn screening for (NBS) for primary carnitine deficiency (PCD) is widely implemented worldwide, however, with poor sensitivity. This study aimed to evaluate the feasibility of improving the screening using second-tier genetic assay. Methods An Agena iPLEX assay was developed to identify 17 SLC22A5 mutations in the Chinese populations, then this assay was applied in NBS for second-tier mutation screening of newborns with low free carnitine (C0) levels. Results The Agena iPLEX assay was successfully established and performed in second-tier genetic screening. A total of316 (0.15%) residual NBS-positive specimens were subjected to second-tier genetic screening. Twenty screen-positive newborns harbored biallelic mutations in SLC22A5 gene, 99 screen-carriers with one mutation, and 197 screen-negative newborns with no mutation identified. Among 99 carriers, four newborns were found with a second disease-causing SLC22A5mutation by further genetic analysis. Four newborns were found with persistently low C0 levels among 197 screen-negatives, further genetic analysis revealed that one newborn with two novel SLC22A5 pathogenic variants. In total, 25 newborns were diagnosed with PCD, for a positive predictive value of 7.91% (25/316). The incidence of PCD in Quanzhou was estimated at 1:8191. Conclusion Data from this study revealed that 24% (6/25) of PCD cases would have been missed by conventional NBS. The high throughput iPLEX assay is a powerful tool for PCD genotyping. The incorporation of second-tier genetic screening into NBS program could increase PCD detection, however, further studies are needed to optimize the workflow of new screening algorithm.