Analysis of External Quality Assessment of Maternal Serum Prenatal Screening for Down Syndrome in the First Trimester in China

Background: We analyzed the 2019 external quality assessment (EQA) results to evaluate the analytical performance of maternal serum prenatal screening for Down Syndrome (DS) in the first trimester in China. Methods: In each round, five lyophilized EQA samples with detailed clinical information were distributed to participants and used to test the concentration of human chorionic gonadotropin free beta subunits (free beta-HCG) and pregnancy-associated plasma protein-A (PAPP-A) to calculate the risk value of DS. The robust coefficient of variability (CV) was calculated or test results for free beta-HCG and PAPP-A using analytes and major measurement platforms. For DS risk values, the robust CV was calculated using a professional calculation platform. Failed EQA results were analyzed using serum marker testing results and DS risk values. Results: EQA results were collected from 242 laboratories in round 1 and 239 laboratories in round 2. Total acceptable rates of testing results for free beta-HCG and PAPP-A ranged from 95.04% to 97.91%. Overall acceptable rates of DS risk values ranged from 97.52% to 97.90%. The proportion of laboratories exhibiting satisfactory performance was higher in round 2 than in round 1 for serum marker testing results and DS risk values. The robust CV for risk values for each sample were significantly higher than those of serum markers. Three EQA result failure types were found, including result reporting errors, serum marker concentration testing errors, and DS risk calculation errors. Conclusions: The analytical performance of maternal serum prenatal screening for DS in the first trimester in China can be improved further.