[Retrospective analysis of quality results of mid-trimester serum screening in China from 2019 to 2023].

<b>Objective:</b> To analyze the quality level of maternal mid-trimester serum prenatal screening in China from 2019 to 2023. <b>Methods:</b> A questionnaire survey was conducted to collect information from laboratories participating in the National Health Commission's Clinical Laboratory Center inter-laboratory quality assessment program for prenatal screening from 2019 to 2023. The collected data included screening protocols, detection methods, testing systems, and monthly laboratory screening quality indicators. The Chi-square test was used to compare the initial screening positive rates among different screening protocols, provinces, detection methods, and testing systems. A log-transformed linear regression analysis was performed to evaluate the relationship between the average annual sample size and the out-of-control rate of various median multiple of the median (mMoM) values. <b>Results:</b> This study included 806 laboratories from 29 provinces (including autonomous regions and municipalities). The five-year average out-of-control rates for mMoM values across indicators ranged from 15.8% to 31.3%. The initial positive rates of dual, triple, and quadruple screening protocols were statistically different (<i>χ</i>²=760.2, <i>P</i><0.001). The initial positive rates across different provinces ranged from 4.7% to 10.3%, with statistically significant differences (<i>χ</i>²=35 388.0, <i>P</i><0.001). There were also statistically significant differences in initial positive rates between different testing systems (<i>χ</i>²=2 493.2, <i>P</i><0.001). Testing systems using chemiluminescence methods had significantly higher initial positive rates compared to systems using time-resolved fluorescence methods (7.2% vs. 6.5%, <i>χ</i>²=533.6, <i>P</i><0.001). Log-linear regression analysis showed that testing systems with larger annual average sample sizes had lower out-of-control rates for mMoM values (AFP: <i>β</i>=-0.100, <i>P</i>=0.005; hCG: <i>β</i>=-0.123, <i>P</i>=0.008; uE3: <i>β</i>=-0.139, <i>P</i>=0.007). <b>Conclusion:</b> There are significant differences in the quality of maternal mid-trimester serum screening across different detection methods, testing systems and provinces in China.