A five-year retrospective analysis of a national external quality assessment program for urinary organic acid analysis in newborn screening for inherited metabolic disorders in China.

This article evaluates the impact of a national external quality assessment (EQA) program, organized by the National Center for Clinical Laboratories (NCCL) in China from 2019 to 2023, on standardizing urinary organic acid analysis using gas chromatography-mass spectrometry (GC-MS) for diagnosing inherited metabolic disorders (IMDs) in newborn screening. The study found that participation in the EQA scheme increased steadily, with significant improvements in measurement precision and reduced regional disparities among laboratories across eastern, central, and western China. Laboratories employing organic acid extraction methods and authorized Newborn Screening Centers (NBSCs) generally demonstrated better performance than those using non-extraction methods or non-NBSCs. The findings underscore the role of EQA programs in enhancing laboratory testing quality and suggest future efforts should focus on expanding participation, optimizing sample preparation protocols, and integrating quantitative with diagnostic capability assessments to further improve IMD diagnosis accuracy.