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.

ObjectivesUrinary organic acid analysis is crucial for diagnosing inherited metabolic disorders (IMDs). This study assesses the impact of an external quality assessment (EQA) scheme on standardizing urinary organic acid detection in China from 2019 to 2023.MethodsThis retrospective longitudinal study analysed data from the NCCL-E-25 EQA scheme for urinary organic acid analysis using gas chromatography-mass spectrometry (GC-MS). Ten batches of EQA data over 5 years were included, focussing on eight key organic acid metabolites. Robust statistical methods were used to evaluate laboratory performance, including regional variations, sample preparation methods, and laboratory types.ResultsParticipating laboratories increased from 43 in 2019 to 76 in 2023, with high participation rates (median 94.74%). All eight target compounds showed significant reductions in robust coefficient of variation (CV) over time. Regional performance disparities narrowed, converging by 2022-2023. Extraction preparation methods generally outperformed non-extraction methods. Newborn Screening Centers (NBSCs) demonstrated lower robust CVs compared to non-NBSCs.ConclusionsThe EQA scheme effectively improved and standardized laboratory testing quality nationwide, particularly benefiting central and western regions. The study highlights the importance of standardized protocols and continuous improvement in enhancing IMD diagnostic accuracy. Future efforts should focus on encouraging wider participation, especially from underrepresented regions, and integrating quantitative and diagnostic capability assessments to comprehensively evaluate laboratory performance.